AvalonBay Communities 424B5 Prospectus supplement for primary offering

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Filed Pursuant to Rule 424(b)(5)
Registration No. 333-187132

PROSPECTUS SUPPLEMENT
(To Prospectus dated March 8, 2013)

7,870,000 Shares

COMMON STOCK

This is a public offering of 7,870,000 shares of common stock of AvalonBay Communities, Inc. The selling stockholder identified in this prospectus supplement is offering all of the shares offered hereby. We will not receive any of the proceeds from the sale of the shares of common stock by the selling stockholder. We will pay the expenses, other than underwriting discounts and commissions and certain other expenses, associated with the sale of shares by the selling stockholder.

Our common stock is listed on the New York Stock Exchange under the symbol "AVB." On May 22, 2013, the last reported sale price of our common stock on the New York Stock Exchange was $138.56 per share.

Investing in our common stock involves risks. See "Risk Factors" beginning on page S-1 of this prospectus supplement and page 2 of the accompanying prospectus.

PRICE $137.00 PER SHARE

	Price to Public	Underwriting Discounts and Commissions	Proceeds to the Selling Stockholder, Before Expenses

Per Share	$137.00	$0.33	$136.67
Total	$1,078,190,000	$2,597,100	$1,075,592,900

The Securities and Exchange Commission and state securities regulators have not approved or disapproved these securities, or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriter expects to deliver the shares of common stock to purchasers on or about May 28, 2013.

Goldman, Sachs & Co.

The date of this prospectus supplement is May 22, 2013.

Table of Contents

TABLE OF CONTENTS


Prospectus Supplement
Risk Factors		S-1
Forward-Looking Statements		S-2
The Company		S-3
Recent Developments		S-4
The Offering		S-4
Use of Proceeds		S-4
Selling Stockholder		S-5
Underwriting		S-6
Legal Matters		S-13
Experts		S-13
Where You Can Find More Information and Documents Incorporated By Reference		S-13
Prospectus
About this Prospectus		1
Where You Can Find More Information		1
Risk Factors		2
Forward-Looking Statements		17
About AvalonBay Communities, Inc.		19
About This Offering		20
Use of Proceeds		20
Selling Stockholders		21
Plan of Distribution		22
Description of Common Stock		25
Limits on Ownership of Stock		26
Federal Income Tax Considerations and Consequences of Your Investment		29
Experts		45
Legal Matters		45

When we refer to "AvalonBay," "the Company," "we," "us," or "our" or similar expressions in this prospectus supplement, we mean AvalonBay Communities, Inc. and its subsidiaries.

This prospectus supplement is a supplement to the accompanying prospectus. If information in this prospectus supplement is inconsistent with the prospectus, this prospectus supplement will apply and supersede the information in the prospectus. It is important for you to read and carefully consider all information contained in this prospectus supplement, the accompanying prospectus and any related free writing prospectus prepared by us or on our behalf. You should also read and carefully consider the information in the documents we have referred you to in "Where You Can Find More Information and Documents Incorporated By Reference."

You should rely only on the information contained or incorporated by reference in this prospectus supplement, the accompanying prospectus and any related free writing prospectus prepared by us or on our behalf. We and the selling stockholder have not, and the underwriters have not, authorized any other person to provide you with different or additional information. If anyone provides you with different or additional information, you should not rely on it. This prospectus supplement, the accompanying prospectus and any related free writing prospectus prepared by us or on our behalf is not an offer to sell or the solicitation of an offer to buy any securities other than the registered shares to which they relate, nor is this prospectus supplement, the accompanying prospectus or any related free writing prospectus prepared by us or on our behalf an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation

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in such jurisdiction. You should assume that the information contained or incorporated by reference in this prospectus supplement, the accompanying prospectus and any related free writing prospectus prepared by us or on our behalf is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates. When the selling stockholder or the underwriters deliver this prospectus supplement, the accompanying prospectus or any related free writing prospectus prepared by us or on our behalf or make a sale pursuant to this prospectus supplement, the accompanying prospectus or any related free writing prospectus prepared by us or on our behalf, neither we, the selling stockholder nor any underwriter is implying that the information is current as of the date of the delivery or sale.

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RISK FACTORS

In addition to the other information contained in this prospectus supplement and the accompanying prospectus, you should carefully consider the risks described in the accompanying prospectus under the heading "Risk Factors" and any additional information and risk factors described in the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, including (i) our Annual Report on Form 10-K, (ii) our Quarterly Reports on Form 10-Q and (iii) any other documents we file with the Securities and Exchange Commission after the date of this prospectus supplement that are deemed incorporated by reference in this prospectus supplement before making an investment decision. These risks are not the only risks we face. Additional risks not presently known to us or that we currently deem immaterial may also adversely affect our business operations. These risks could adversely affect, among other things, our business, financial condition or results of operations, and could cause the trading price of our common stock to decline, resulting in the loss of all or part of your investment.

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FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and any related free writing prospectus, including the information incorporated by reference, contain statements that are forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. You can identify forward-looking statements by the use of the words "believe," "expect," "anticipate," "intend," "estimate," "assume," "project," "plan," "may," "shall," "will," "outlook" and other similar expressions that predict or indicate future events and trends and which do not relate to historical matters. We cannot assure the future results or outcome of the matters described in these statements; rather, these statements merely reflect our current expectations of the approximate outcomes of the matters discussed. You should not rely on forward-looking statements because they involve known and unknown risks, uncertainties and other factors, some of which are beyond our control. In addition, these forward-looking statements represent our estimates and assumptions only as of the date of this prospectus supplement. We do not undertake to update these forward-looking statements, and therefore they may not represent our estimates and assumptions after the date of this prospectus supplement. These risks, uncertainties and other factors, which are described below and under the headings "Risk Factors" and "Forward-Looking Statements" in the accompanying prospectus and in the documents incorporated by reference, may cause our actual results, performance or achievements to differ materially from the anticipated future results, performance or achievements expressed or implied by these forward-looking statements.

Some of the factors that could cause our actual results, performance or achievements to differ materially from those expressed or implied by these forward-looking statements include, but are not limited to, the following:

•: we may fail to secure development opportunities due to an inability to reach agreements with third-parties to obtain land at attractive prices or to obtain desired zoning and other local approvals;
•: we may abandon or defer development opportunities for a number of reasons, including changes in local market conditions which make development less desirable, increases in costs of development, increases in the cost of capital or lack of capital availability, resulting in losses;
•: construction costs of a community may exceed our original estimates;
•: we may not complete construction and lease-up of communities under development or redevelopment on schedule, resulting in increased interest costs and construction costs and a decrease in our expected rental revenues;
•: occupancy rates and market rents may be adversely affected by competition and local economic and market conditions which are beyond our control;
•: financing may not be available on favorable terms or at all, and our cash flows from operations and access to cost effective capital may be insufficient for the development of our pipeline which could limit our pursuit of opportunities;
•: our cash flows may be insufficient to meet required payments of principal and interest, and we may be unable to refinance existing indebtedness or the terms of such refinancing may not be as favorable as the terms of existing indebtedness;
•: we may be unsuccessful in our management of investment funds and joint ventures, or any REIT vehicles that are used with any specific fund or joint venture, described in greater detail in our reports filed with the SEC that are incorporated by reference into this prospectus supplement; and
•: we may be unsuccessful in managing changes in our portfolio composition, including operating outside of our core markets as a result of the Archstone Portfolio Acquisition (as defined in the accompanying prospectus).

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THE COMPANY

AvalonBay Communities, Inc. is a real estate investment trust (a "REIT"), and an S&P 500 Index company that owns one of the largest portfolios of high-quality multifamily communities in the United States. We are focused on the development, redevelopment, acquisition, operation and management of apartment communities in high barrier-to-entry markets in the Northeast, Mid-Atlantic and West Coast regions of the United States.

At March 31, 2013, we owned or held a direct or indirect ownership interests in:

•: 245 operating apartment communities containing 73,477 apartment homes in 12 states and the District of Columbia, of which five communities containing 2,164 apartment homes were under reconstruction;
•: 27 communities under construction that are expected to contain an aggregate of 7,802 apartment homes when completed; and
•: land or rights to land in which the Company expects to develop an additional 42 communities that, if developed as expected, will contain an estimated 12,040 apartment homes.

The information about our ownership interests above excludes real estate investments owned indirectly through three limited liability company agreements through which we and Equity Residential acquired certain assets of Archstone Enterprise LP (which has changed its name to Jupiter Enterprise LP) that we and Equity Residential plan to divest to third parties or to ourselves and/or Equity Residential over time. See "About AvalonBay Communities, Inc.—The Archstone Portfolio Acquisition" in the accompanying prospectus and the additional information in the documents incorporated by reference in this prospectus supplement and in the accompanying prospectus.

Our principal financial goal is to increase long-term shareholder value through our integrated multifamily investment and operating platform by pursuing a strategy of being leaders in market research and capital allocation and delivering a range of multifamily offerings tailored to serve the needs of the most attractive customer segments in the best-performing submarkets of the U.S. We pursue this strategy through three brand offerings, each targeting a different customer segment and price point. Our "Avalon" brand, our core offering, focuses on upscale apartment living and high-end amenities and services in urban and suburban markets. Our "AVA" brand is designed for people who want to live in or near urban neighborhoods and in close proximity to public transportation, services, shopping and night-life.AVA apartments are generally smaller, with many engineered for roommate living, featuring modern design and a technology focus. Our "Eaves by Avalon" brand is designed for renters who seek quality apartment living, often in a suburban setting, with practical amenities and services at a more modest price point.

AvalonBay elected to qualify as a REIT for federal income tax purposes for the taxable year ended December 31, 1994, and has not terminated or revoked such election. As a REIT, with limited exceptions, we will not be taxed under federal and certain state income tax laws at the corporate level on our net income to the extent net income is distributed to our stockholders. We have historically made sufficient distributions to avoid tax on retained income, and we intend to make sufficient distributions to avoid income tax at the corporate level. While we believe that we are organized and qualified as a REIT and we intend to operate in a manner that will allow us to continue to qualify as a REIT, there can be no assurance that we will be successful in this regard. Qualification as a REIT involves the application of highly technical and complex provisions of the Internal Revenue Code of 1986, as amended (the "Code"), for which there are limited judicial and administrative interpretations and involves the determination of a variety of factual matters and circumstances not entirely within our control.

Our principal executive offices are located at Ballston Tower, 671 N. Glebe Road, Suite 800, Arlington, Virginia 22203, Attention: Chief Financial Officer. Our telephone number is 703-329-6300. Our website is located atwww.avalonbay.com. Information on our website is not deemed to be a part of this prospectus supplement or the accompanying prospectus.

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RECENT DEVELOPMENTS

The stockholders of the Company approved an amendment to the Company's Amended and Restated Articles of Incorporation, as amended, at the Company's Annual Meeting of Stockholders on May 22, 2013. The amendment, which was effective upon filing with, and acceptance for record by, the Maryland Department of Assessments and Taxation on May 22, 2013, increased the authorized number of shares of the Company's common stock by 140 million shares from 140 million shares to a total of 280 million shares.

THE OFFERING


Issuer		AvalonBay Communities, Inc.
Common stock offered by the selling stockholder		7,870,000 shares.
Common stock outstanding after this offering		129,379,969 shares as of April 30, 2013.
Use of proceeds		The selling stockholder will receive all of the net proceeds from the sale of our common stock in this offering. We will not receive any of the proceeds from the sale of the shares of our common stock by the selling stockholder. See "Use of Proceeds."
NYSE symbol		AVB
Risk Factors		An investment in our common stock involves various risks, and prospective investors should carefully consider the matters discussed under the caption entitled "Risk Factors" in this prospectus supplement and in the accompanying prospectus and the documents incorporated by reference before making a decision to invest in our common stock.

The shares of common stock offered by this prospectus supplement and the accompanying prospectus are currently outstanding shares, and no new shares of common stock will be issued in connection with this offering. Accordingly, there will be no change in the number of shares outstanding as a result of the sale of shares by the selling stockholder in this offering. The number of shares of common stock outstanding as of April 30, 2013 was 129,379,969.

USE OF PROCEEDS

All shares of common stock sold pursuant to this prospectus supplement will be sold by the selling stockholder. We will not receive any of the proceeds from such sales. We will pay (1) the expenses, other than underwriting discounts and commissions and certain other expenses, associated with the sale of shares by the selling stockholder and (2) the registration expenses, including filing fees, printing fees and fees of our counsel and other advisers.

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SELLING STOCKHOLDER

When we refer to the "selling stockholder" in this prospectus supplement we mean the stockholder listed in the table below and its pledgees, donees, transferees or other successors in interest. The following table sets forth the number of shares of common stock owned by the selling stockholder prior to this offering, the number of shares of common stock to be offered for sale by the selling stockholder in this offering, the number of shares of common stock to be owned by the selling stockholder after completion of the offering and the percentage of our outstanding shares of common stock owned by the selling stockholder prior to this offering and to be owned after the completion of this offering.

Beneficial ownership is determined in accordance with the rules of the SEC and includes voting or investment power with respect to the securities. The percentage of shares beneficially owned prior to the offering is based on 129,379,969 shares of our common stock outstanding as of April 30, 2013. Except as otherwise indicated, the selling stockholder has sole voting and investment power with respect to all shares of capital stock held by it. The address of the selling stockholder is 1271 Avenue of the Americas, New York, New York 10020.

	Shares Beneficially Owned Before This Offering			Shares Beneficially Owned After This Offering

	Shares Beneficially Owned Before This Offering		Shares Offered Hereby	Shares Beneficially Owned After This Offering
Selling Stockholder	Number	Percentage	Shares Offered Hereby	Number	Percentage
Jupiter Enterprise LP(1)	14,889,706	11.5%	7,870,000	7,019,706	5.4%

(1): The shares of common stock are directly owned by Jupiter Enterprise LP ("Jupiter"). Jupiter is an indirect subsidiary of Lehman Brothers Holdings Inc. ("LBHI"). Under SEC rules regarding beneficial ownership, LBHI may be deemed to have voting and investment power over the shares of common stock shown in the table above. Lehman Brothers Holdings Inc. Plan Trust (the "Plan Trust") is the sole stockholder of LBHI. Despite this ownership, the Plan Trust does not have any voting or investment discretion with respect to the shares of common stock shown in the table above.

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UNDERWRITING

The selling stockholder is offering the shares of common stock described in this prospectus supplement through the underwriter. Subject to the terms and conditions described in an underwriting agreement among us, the selling stockholder and the underwriter, the underwriter has agreed to purchase, and the selling stockholder has agreed to sell to the underwriter, Goldman, Sachs & Co., shares of common stock at a price of $136.67 per share, which will result in $1,075,592,900.00 of proceeds to the selling stockholder before expenses.

Subject to the terms and conditions of the underwriting agreement, the underwriter is committed to purchase all of the shares of common stock offered by the selling stockholder if it purchases any such shares. The underwriting agreement provides that the obligation of the underwriter to pay for and accept delivery of the shares of common stock offered by this prospectus supplement are subject to the approval of certain legal matters by its counsel and to other conditions.

The underwriter initially proposes to offer the shares for sale at the offering price set forth on the cover page of this prospectus supplement.

Sales of shares outside the United States may be made by affiliates of the underwriter. The offering of the shares by the underwriter is subject to receipt and acceptance and subject to the underwriter's right to reject any order in whole or in part.

The estimated offering expenses payable by us are approximately $125,000.

We have agreed that, without the prior written consent of the underwriter, we will not, during the period beginning on the date of this prospectus supplement and ending 30 days thereafter:

•: offer, pledge, announce the intention to sell, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise transfer or dispose of, directly or indirectly, any shares of common stock or any securities convertible into or exercisable or exchangeable for common stock; or
•: enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the common stock;

whether any such transaction described above is to be settled by delivery of common stock or such other securities, in cash or otherwise.

The restrictions described in the immediately preceding paragraph do not apply to:

•: the issuance by us of shares of common stock upon the exercise of an option or a warrant or the conversion or redemption of a security (including, without limitation, downREIT units of limited partnership;
•: the grant of options or the issuance of shares of common stock by us to employees, officers, directors, advisors or consultants in the ordinary course pursuant to any current or future employee or director stock option, incentive or benefit plan, employee stock purchase, long-term incentive plan, deferred compensation plan or ownership plan or dividend investment plan; or
•: the issuance of shares under our dividend reinvestment and stock purchase plan;
•: the issuance of shares of common stock in connection with acquisitions, provided that such acquisitions do not in the aggregate exceed 10% of our fully diluted common stock as of the date of this prospectus supplement, and provided further that the recipient agrees to the above restrictions on transfer of acquisition shares for the remainder of the 30 day period referred to above.

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Our directors and executive officers have agreed that they will not, without, in each case, the prior written consent of the underwriter, during the period beginning on the date of this prospectus supplement and ending 30 days thereafter:

•: offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend or otherwise transfer or dispose of, directly or indirectly, any of our shares of common stock or any securities convertible into or exercisable or exchangeable for shares of our common stock; or
•: enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of shares of our common stock, whether any transaction described above is to be settled by delivery of our shares or other securities, in cash or otherwise.

The restrictions described in the above paragraphs relating to certain of our directors and executive officers do not apply to:

•: the exercise for cash of any stock option, provided that all shares issued upon exercise are subject to the lock-up agreement;
•: the delivery to the Company of shares for cancellation or the withholding by the Company of shares to pay the exercise price of any stock option under a Company plan or to pay taxes upon the exercise or vesting of any equity awards granted by the Company to the director or executive officer;
•: sales pursuant to plans complying with the safe harbor provided by Rule 10b5-1 promulgated under the Exchange Act that were entered into prior to the date of this prospectus supplement;
•: acquisitions of shares of our common stock or other securities in the open market after the completion of this public offering;
•: a foreclosure by a bona fide lender upon shares which on the date hereof are pledged to secure a loan, provided that such directors or executive officers used reasonable efforts to prevent such foreclosure; or
•: any transfer of our common stock as a bona fide gift or gifts, provided that, in the case of a gift of greater than 7,500 shares of our common stock or a gift to a donee that is not a tax exempt charitable organization or foundation, the donee or donees thereof agree to be bound in writing to the above restrictions for the remainder of the 30 day period referred to above.

The selling stockholder has agreed that it will not, without, in each case, the prior written consent of the underwriter, during the period beginning on the date of this prospectus supplement and ending 60 days thereafter:

•: offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend or otherwise transfer or dispose of, directly or indirectly, any of our shares of common stock or any securities convertible into or exercisable or exchangeable for shares of our common stock; or
•: enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of shares of our common stock, whether any transaction described above is to be settled by delivery of our shares or other securities, in cash or otherwise.

The restrictions described in the above paragraphs relating to the selling stockholder do not apply to:

•: the sale to the underwriter of the shares of common stock offered by this prospectus supplement; or

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•: the distribution or transfer of the shares of common stock to entities affiliated with the selling stockholder, provided that the recipient agrees to the above restrictions on transfer of the acquired shares of common stock for the remainder of the 60 day period referred to above.

In connection with this offering, the underwriter may engage in stabilizing transactions, which involves making bids for, purchasing and selling shares of common stock in the open market for the purpose of preventing or retarding a decline in the market price of the common stock while this offering is in progress. These stabilizing transactions may include making short sales of the common stock, which involves the sale by the underwriter of a greater number of shares of common stock than it is required to purchase in this offering, and purchasing shares of common stock on the open market to cover positions created by short sales.

The underwriter has advised us that, pursuant to Regulation M of the Securities Act, it may also engage in other activities that stabilize, maintain or otherwise affect the price of the common stock.

These activities may have the effect of raising or maintaining the market price of the common stock or preventing or retarding a decline in the market price of the common stock, and, as a result, the price of the common stock may be higher than the price that otherwise might exist in the open market. If the underwriter commences these activities, it may discontinue them at any time. The underwriter may carry out these transactions on the New York Stock Exchange, in the over-the-counter market or otherwise.

Our common stock is quoted on the New York Stock Exchange under the symbol "AVB."

We, the selling stockholder and the underwriter have agreed to indemnify each other against certain liabilities, including liabilities under the Securities Act.

This prospectus supplement or accompanying prospectus in electronic format may be made available on the web sites maintained by the underwriter or by selling group members, if any, participating in the offering, and the underwriter may distribute prospectuses electronically. Other than the prospectus supplement or accompanying prospectus in electronic format, the information on any of these websites and any other information contained on a website maintained by an underwriter or selling group member is not part of this prospectus supplement or accompanying prospectus. The underwriter may agree to allocate a number of shares to underwriter and selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the underwriter or selling group members that make Internet distributions on the same basis as other allocations.

In the ordinary course of business, the underwriter and/or its affiliates have engaged, and may in the future engage, in commercial banking or investment banking transactions with us and our affiliates for which they have received, and will in the future receive, customary compensation.

An affiliate of Goldman, Sachs & Co. holds a commitment under our $1,300,000,000 unsecured revolving credit facility. Additionally, an affiliate of Goldman, Sachs & Co. acts as a Documentation Agent under this credit facility.

In addition, the underwriter and its affiliates have provided, and may in the future provide, construction loans, letter of credit facilities and other credit-related arrangements to us. The underwriter and its affiliates have participated in, and may in the future participate in, debt offerings for us. The underwriter and its affiliates have provided, and may in the future provide, various investment banking, commercial banking, financial advisory, brokerage and other services to us and our affiliates for which services they have received, and may in the future receive, customary fees. In the ordinary course of their various business activities, the underwriter and its affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers and such investment and securities activities may involve securities and/or instruments of the

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Company. The underwriter and its affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Notice to Prospective Investors in the European Economic Area

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive, as defined below (each, a "Relevant Member State"), an offer of shares to the public may not be made in that Relevant Member State, except that, with effect from and including the date on which the Prospectus Directive is implemented in that Relevant Member State, an offer of shares to the public may only be made in that Relevant Member State:

•: to any legal entity which is a qualified investor as defined in the Prospectus Directive;
•: to fewer than 100 or, if the Relevant Member State has implemented the relevant provisions of the 2010 PD Amending Directive, 150 natural or legal persons (other than qualified investors as defined in the Prospectus Directive), subject to obtaining the prior written consent of the representatives for any such offer; or
•: in any other circumstances falling within Article 3(2) of the Prospectus Directive,

provided that no such offer of shares shall require us or the underwriter to publish a prospectus pursuant to Article 3 of the Prospective Directive.

For the purposes of this provision, the expression "an offer of shares to the public" in relation to the shares in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the shares to be offered so as to enable an investor to decide to purchase or subscribe the shares, as the same may be varied in that Relevant Member State by any measure implementing the Prospectus Directive in that Relevant Member State; the expression "Prospectus Directive" means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in that Relevant Member State), and includes any relevant implementing measure in each Relevant Member State: and the expression "2010 PD Amending Directive" means Directive 2010/73/EU.

Each purchaser of the shares described in this prospectus supplement located within a Relevant Member State will be deemed to have represented, acknowledged and agreed to and with us and the underwriter that it is a "qualified investor" within the meaning of Article 2(1)(e) of the Prospectus Directive.

We have not authorized and do not authorize the making of any offer of shares through any financial intermediary on our behalf, other than offers made by the underwriter with a view to the final placement of the shares as contemplated in this prospectus supplement. Accordingly, no purchaser of the shares, other than the underwriter, is authorized to make any further offer of the shares on behalf of us or the underwriter.

Notice to Prospective Investors in the United Kingdom

The applicable provisions of the United Kingdom's Financial Services and Markets Act 2000 (the "FSMA") must be complied with in respect of anything done in relation to the shares in, from or otherwise involving the United Kingdom.

Any invitation or inducement to engage in investment activity (within the meaning of Section 21 of the FSMA), in connection with the issue or sale of the shares, has only been and will only be communicated or caused to be communicated in circumstances in which Section 21(1) of the FSMA does not apply to us.

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Without limitation to the other restrictions referred to herein, this prospectus supplement and any documents and/or materials relating to the shares are directed only at and distributed only to persons located or resident outside the United Kingdom or, if located or resident in the United Kingdom, to (i) investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the "Order"), (ii) high net worth companies, unincorporated associations and other persons falling within Article 49(2) (a) to (d) of the Order or (iii) any other persons to whom this prospectus supplement and such other documents or materials may otherwise lawfully be communicated in accordance with the Order. Without limitation to the other restrictions referred to herein, any investment or investment activity to which this prospectus supplement relates is available only to, and will be engaged in only with, such persons, and persons within the United Kingdom who receive this communication (other than persons who fall within (i) to (iii) above) should not rely or act upon this communication.

Notice to Prospective Investors in Hong Kong

The shares may not be offered or sold to persons in Hong Kong by means of any document other than (i) to persons whose ordinary business is to buy or sell shares or debentures, whether as principal or agent, or (ii) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong), or (iii) to "professional investors" within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iv) in other circumstances which do not result in the document being a "prospectus" within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong) and no advertisement, invitation or document relating to the shares may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to shares which are or are intended to be disposed of only to persons outside Hong Kong or only to "professional investors" within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Notice to Prospective Investors in Japan

The shares offered in this prospectus supplement have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) (the "Financial Instruments and Exchange Law"). The shares have not been offered or sold and will not be offered or sold, directly or indirectly, in Japan or to or for the account or benefit of any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity incorporated or organized under the laws of Japan), or to, or for the account or benefit of, others for re-offering or resale, directly or indirectly, in Japan or to, or for the account or benefit of, any resident of Japan, except (i) pursuant to an exemption from the registration requirements of the Financial Instruments and Exchange Law and (ii) otherwise in compliance with the Financial Instruments and Exchange Law and any other applicable requirements of Japanese law.

Notice to Prospective Investors in Singapore

Neither this prospectus supplement nor the accompanying prospectus has been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement, the accompanying prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the shares may not be circulated or distributed, nor may the shares be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the "SFA"), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with

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the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

Where the shares are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

•: a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or
•: a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

shares, debentures and units of shares and debentures of that corporation or the beneficiaries' rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the shares pursuant to an offer made under Section 275 of the SFA except:

•: to an institutional investor under Section 274 of the SFA or to a relevant person defined in Section 275(2) of the SFA, or to any person pursuant to an offer under Section 275(1A) of the SFA (an offer that is made on terms that such shares, debentures and units of shares and debentures of that corporation or such rights and interest in that trust are acquired at a consideration of not less than $200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets), and in accordance with the conditions specified in Section 275 of the SFA;
•: where no consideration is or will be given for the transfer; or
•: where the transfer is by operation of law.

Notice to Prospective Investors in The Netherlands

The offer in The Netherlands of the shares included in this offering is exclusively limited to persons who trade or invest in securities in the conduct of a profession or business (which include banks, stockbrokers, insurance companies, pension funds, other institutional investors and finance companies and treasury departments of large enterprises).

Notice to Prospective Investors in Switzerland

We have not and will not register with the Swiss Financial Market Supervisory Authority ("FINMA") as a foreign collective investment scheme pursuant to Article 119 of the Federal Act on Collective Investment Scheme of 23 June 2006, as amended ("CISA"), and accordingly the shares being offered pursuant to this prospectus supplement have not and will not be approved, and may not be licensable, with FINMA. Therefore, the shares have not been authorized for distribution by FINMA as a foreign collective investment scheme pursuant to Article 119 CISA and the shares offered hereby may not be offered to the public (as this term is defined in Article 3 CISA) in or from Switzerland. The shares may solely be offered to "qualified investors," as this term is defined in Article 10 CISA, and in the circumstances set out in Article 3 of the Ordinance on Collective Investment Scheme of 22 November 2006, as amended ("CISO"), such that there is no public offer. Investors, however, do not benefit from protection under CISA or CISO or supervision by FINMA. This prospectus supplement, the accompanying prospectus and any other materials relating to the shares are strictly personal and confidential to each offeree and do not constitute an offer to any other person. This prospectus supplement and the accompanying prospectus may only be used by those qualified investors to whom it has been handed out in connection with the offer described herein and may neither directly or indirectly be distributed or made available to any person or entity other than its recipients. It may

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not be used in connection with any other offer and shall in particular not be copied and/or distributed to the public in Switzerland or from Switzerland. This prospectus does not constitute an issue prospectus as that term is understood pursuant to Article 652a and/or 1156 of the Swiss Federal Code of Obligations. We have not applied for listing of the shares on the SIX Swiss Exchange or any other regulated securities market in Switzerland, and consequently, the information presented in this prospectus does not necessarily comply with the information standards set out in the listing rules of the SIX Swiss Exchange and corresponding prospectus schemes annexed to the listing rules of the SIX Swiss Exchange.

Notice to Prospective Investors in the Dubai International Financial Centre

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority ("DFSA"). This prospectus supplement is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for the prospectus supplement. The shares to which this prospectus supplement relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the shares offered should conduct their own due diligence on the shares. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

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LEGAL MATTERS

Goodwin Procter LLP, Boston, Massachusetts, will pass upon certain matters relating to this offering for us. Certain matters will be passed upon for the selling stockholder by Weil, Gotshal & Manges LLP, New York, New York. Certain legal matters will be passed upon for the underwriter by O'Melveny & Myers LLP, San Francisco, California.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements and schedule included in our Annual Report on Form 10-K for the year ended December 31, 2012, and the effectiveness of our internal control over financial reporting as of December 31, 2012, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements and schedule are incorporated by reference in reliance on Ernst & Young LLP's reports, given on their authority as experts in accounting and auditing.

The combined statement of revenue and certain expenses of the Archstone Portfolio for the year ended December 31, 2012, appearing in our Current Report on Form 8-K filed with the SEC on February 26, 2013, has been incorporated by reference herein in reliance upon the report of KPMG LLP, independent auditors, incorporated by reference herein, and upon authority of such firm as experts in accounting and auditing. KPMG LLP's report on the combined statement of revenue and certain expenses of the Archstone Portfolio contains a paragraph that states that the combined statement of revenue and certain expenses was prepared for the purpose of complying with the rules and regulations of the SEC, as described in Note 1 to the combined statement of revenue and certain expenses, and it is not intended to be complete presentation of the Archstone Portfolio's revenue and expenses.

WHERE YOU CAN FIND MORE INFORMATION AND DOCUMENTS
INCORPORATED BY REFERENCE

We are subject to the information requirements of the Exchange Act, and in accordance with the Exchange Act, we file annual, quarterly, and current reports, proxy statements, and other information with the SEC. You may read and copy any document we file at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You may call the SEC at 1-800-SEC-0330 for further information on the operation of the Public Reference Room. Our SEC filings are also available to the public from the SEC's website athttp://www.sec.gov. In addition, you may read our SEC filings at the offices of the New York Stock Exchange, which is located at 20 Broad Street, New York, New York 10005.

We have a website located athttp://www.avalonbay.com. The information on our website is not a part of this prospectus supplement or the accompanying prospectus.

The information incorporated by reference herein is an important part of this prospectus supplement. Any statement contained in a document which is incorporated by reference in this prospectus supplement is automatically updated and superseded if information contained in this prospectus supplement, or information that we have filed or later file with the SEC prior to the termination of this offering, modifies or replaces this information. We are incorporating by reference the documents listed below, which were previously filed with the SEC:

•: Annual Report on Form 10-K for the year ended December 31, 2012, filed on February 22, 2013;
•: Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2013, filed on May 10, 2013;

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•: Current Reports on Form 8-K filed on February 26, 2013; March 5, 2013; March 18, 2013; and May 22, 2013; and Form 8-K/A filed on March 7, 2013;
•: Definitive Proxy Statement filed on April 8, 2013;
•: the description of the AvalonBay Communities, Inc. common stock in AvalonBay Communities, Inc.'s Registration Statement on Form 8-B filed on June 8, 1995; and
•: all documents filed by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus supplement and prior to the termination of this offering, except as to any portion of any future report or document that is not deemed filed under such provisions.

Upon request, we will provide, without charge, to each person, including any beneficial owner, to whom a copy of this prospectus supplement is delivered a copy of the documents incorporated by reference in this prospectus supplement. You may request a copy of these filings, and any exhibits we have specifically incorporated by reference as an exhibit in this prospectus supplement, by writing or telephoning us at the following:

AvalonBay Communities, Inc.
671 N. Glebe Road, Suite 800
Arlington, VA 22203
Attention: Investor Relations
(703) 329-6300

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Prospectus

AVALONBAY COMMUNITIES, INC.

14,889,706 Shares of Common Stock

This prospectus relates to the potential resale from time to time by the selling stockholders identified in this prospectus of some or all of 14,889,706 shares of our common stock, or the securities, held by such selling stockholders. The registration of the offer and sale of the securities covered by this prospectus does not necessarily mean that any of the securities will be offered or sold by the selling stockholders.

We will receive no proceeds from any resale of the shares of common stock, but we have agreed to pay certain registration expenses.

The selling stockholders identified in this prospectus (which term as used herein includes their pledgees, donees, transferees, or other successors in interest), may offer the securities from time to time as they may determine directly or through underwriters, broker-dealers or agents and in one or more public or private transactions, on or off the New York Stock Exchange, or NYSE, and at fixed prices, prevailing market prices, at prices related to prevailing market prices or at negotiated prices. If these securities are sold through underwriters, broker-dealers or agents, the selling stockholders will be responsible for underwriting discounts or commissions or agents' commissions. See the sections entitled "Plan of Distribution" and "About this Prospectus" for more information.

Our common stock is listed on NYSE under the symbol "AVB." On March 6, 2013, the closing price of our common stock on the NYSE was $126.23 per share.

We impose certain restrictions on the ownership and transfer of our stock. You should read the information under the section entitled "Restrictions on Ownership and Transfer" in this prospectus for a description of these restrictions.

Investing in our securities involves various risks. Beginning on page 2, we have discussed several "Risk Factors" that you should consider before investing in our securities.

March 8, 2013

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

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About this Prospectus		1
Where You Can Find More Information		1
Risk Factors		2
Forward-Looking Statements		17
About AvalonBay Communities, Inc.		19
About This Offering		20
Use of Proceeds		20
Selling Stockholders		21
Plan of Distribution		22
Description of Common Stock		25
Limits on Ownership of Stock		26
Federal Income Tax Considerations and Consequences of Your Investment		29
Experts		45
Legal Matters		45

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About this Prospectus

This prospectus is part of a registration statement that we filed with the SEC utilizing a shelf registration process. Under this shelf process, the selling stockholders may sell the shares of common stock registered pursuant to the registration statement in one or more offerings. When a selling stockholder elects to make an offer of common stock pursuant to this registration statement, a prospectus supplement, if required, may be distributed that will contain specific information about the terms of that offering. Any required prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and any applicable prospectus supplement together with additional information described below under the heading "Where You Can Find More Information."

Where You Can Find More Information

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any document we file at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You may call the SEC at 1-800-SEC-0330 for further information on the operation of the Public Reference Room. Our SEC filings are also available to the public from the SEC's Web site athttp://www.sec.gov or on our website located athttp://www.avalonbay.com. The information on our website is not a part of this prospectus.

In accordance with Section 2-210 of the Maryland General Corporation Law, our board of directors may authorize the issuance of some or all of the shares of any or all of our classes or series of stock without certificates. In addition, we have the authority to designate and issue more than one class or series of stock having various preferences, conversion and other rights, voting powers, restrictions, limitations as to dividends, qualifications, and terms and conditions of redemption. See "Description of Preferred Stock" and "Description of Common Stock." Our charter imposes limitations on the ownership and transfer of our stock. See "Limits on Ownership of Stock." We will furnish a full statement of the relative rights and preferences of each class or series of our stock which has been so designated and any restrictions on the ownership or transfer of our stock to any stockholder upon request and without charge. Written requests for such copies should be directed to: AvalonBay Communities, Inc., 671 N. Glebe Road, Suite 800, Arlington, Virginia 22203, Attention: Chief Financial Officer.

The SEC allows us to incorporate by reference the information we file with it, which means that we can disclose important information to you by referring you to these documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede the information already incorporated by reference. AvalonBay's SEC file number is 001-12672. We are incorporating by reference the documents listed below, which were previously filed by us with the SEC:

•: Annual Report on Form 10-K for the year ended December 31, 2012 filed on February 22, 2013;
•: Current Report on Form 8-K, filed on February 26, 2013;
•: Current Report on Form 8-K, filed on March 5, 2013, as amended by Current Report on Form 8-K/A, filed on March 7, 2013;
•: the description of the AvalonBay Communities, Inc. common stock in AvalonBay Communities, Inc.'s Registration Statement on Form 8-B filed on June 8, 1995; and
•: all documents filed by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus and prior to the termination of this offering, except as to any portion of any future report or document that is not deemed filed under such provisions.

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You may request a copy of these filings, and any exhibits we have specifically incorporated by reference as an exhibit in this prospectus, at no cost by writing or telephoning us at the following: AvalonBay Communities, Inc., 671 N. Glebe Rd., Suite 800, Arlington, Virginia 22203, Attention: Chief Financial Officer. Our telephone number is 703-329-6300.

This prospectus is part of a registration statement we filed with the SEC. We have incorporated exhibits into this registration statement. You should read the exhibits carefully for provisions that may be important to you.

You should rely only on the information incorporated by reference or provided in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this prospectus or in the documents incorporated by reference is accurate as of any date other than the date on the front of this prospectus or those documents.

Unless the context otherwise requires, all references to "we," "us," "our," "our company," "AvalonBay," or similar expressions in this prospectus refer collectively to AvalonBay Communities, Inc., a Maryland corporation, and its subsidiaries, and their respective predecessor entities for the applicable periods, considered as a single enterprise.

Risk Factors

Before you invest in our securities, you should be aware that there are risks in making the investment, including those described below. You should consider carefully these risk factors together with all of the information included or incorporated by reference in this prospectus before you decide to purchase our securities. This section includes or refers to forward-looking statements. Actual results could differ materially from those anticipated in these forward-looking statements as a result of certain factors, including the risks described in the documents incorporated herein by reference, including (i) our Annual Reports on Form 10-K, (ii) our Quarterly Reports on Form 10-Q and (iii) documents we file with the SEC after the date of this prospectus and which are deemed incorporated by reference in this prospectus. You should refer to the explanation of the qualifications and limitations on forward-looking statements discussed under "Forward-Looking Statements" below.

The intended benefits of the Archstone Portfolio Acquisition may not be realized, which could have a negative impact on the market price of our common stock.

The Archstone Portfolio Acquisition (as defined in "About AvalonBay Communities—The Archstone Portfolio Acquisition"), which we completed on February 27, 2013, poses risks for our ongoing operations, including that:

•: our senior management's attention may be diverted from the management of daily operations to the integration of the Archstone Portfolio Acquisition, including management of assets located outside of our core markets pending disposition, which may disrupt management of our existing business and our relationships with our customers;
•: we may bear costs and expenses associated with any undisclosed or potential liabilities;
•: the Archstone Portfolio Acquisition may not perform as well as we anticipate; and
•: unforeseen difficulties may arise in integrating the Archstone Portfolio Acquisition into our portfolio.

Also, we acquired assets and assumed liabilities in connection with the Archstone Portfolio Acquisition on an "as is" basis with only limited representations from Lehman Brothers Holdings Inc. ("LBHI") surviving after the closing of the Archstone Portfolio Acquisition, which limits our future

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recourse against the seller for breaches of representations, which in turn may expose us to unexpected material losses or expenses in the future.

In addition, our diligence investigations with respect to the assets comprising the Archstone Portfolio Acquisition were more limited than would be the case if we were acquiring individual apartment communities or land parcels, which may also expose us to unexpected material losses or expenses in the future.

As a result of the foregoing, we cannot assure you that the Archstone Portfolio Acquisition will be accretive to us in the near term or at all. Furthermore, if we fail to realize the intended benefits of the Archstone Portfolio Acquisition, the market price of our common stock could decline to the extent that the market price reflects those benefits.

The Archstone Portfolio Acquisition significantly increased the size of our real estate portfolio and related personnel and operating and financial needs, and we may not be successful in integrating the Archstone Portfolio Acquisition into our business.

The Archstone Portfolio Acquisition involves a variety of risks, including potential difficulties in integrating the portfolio, diversions of our management resources, differing levels of management and internal control effectiveness at the acquired entities and other unanticipated problems and liabilities. Any of these risks could adversely affect our financial results and reduce or delay our ability to obtain the expected benefits of the Archstone Portfolio Acquisition.

In addition, the increased need for financial resources that will result from the Archstone Portfolio Acquisition, as well as the diversion of our management resources, may affect our existing development, redevelopment and acquisition portfolios and development rights pipeline. As a result, there may be unexpected delays in the timing of our activities relating to our existing real estate portfolios and development rights pipeline, and we may encounter unexpected costs or we may not succeed in obtaining the expected benefits of our currently expected real estate development, redevelopment and acquisition activities. These issues could also increase our capital requirements, which may require us to issue potentially dilutive equity securities and incur additional debt.

The governance provisions of our joint ventures with Equity Residential could adversely affect our flexibility in dealing with such joint venture assets and liabilities.

In connection with the Archstone Portfolio Acquisition, we created joint ventures with Equity Residential to manage certain of the acquired assets and liabilities. These structures involve participation in the investment by Equity Residential, whose interests and rights may not be the same as ours. Joint ownership of an investment in real estate involves risks not associated with direct ownership of real estate, including the risk that Equity Residential may at any time have economic or other business interests or goals which become inconsistent with our business interests or goals, including inconsistent goals relating to the sale of properties held in the joint ventures or the timing of the termination and liquidation of the joint ventures. Under the joint venture arrangements, neither we nor Equity Residential expect to have the power to control the ventures, and an impasse could occur, which would adversely affect the applicable joint venture and decrease potential returns to us and our investors.

The trading price of our common stock has been and may continue to be subject to wide fluctuations.

The sale price of our common stock on the New York Stock Exchange has fluctuated in recent quarters. Our stock price may fluctuate in response to a number of events and factors, such as those described elsewhere in this "Risk Factors" section and those events described or incorporated by reference in this prospectus supplement.

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We assumed indebtedness in connection with the Archstone Portfolio Acquisition, which may have an adverse effect on our financial condition and results of operations, and our ability to make distributions to our stockholders.

We assumed indebtedness with a fair value of approximately $4.0 billion in connection with the Archstone Portfolio Acquisition, which increased our leverage and the ratio of our net debt to our earnings before interest, tax, depreciation and amortization. There can be no assurance that we will be able to reduce or refinance, over time, to the extent we anticipate, this assumed indebtedness. Therefore, the increase in indebtedness could have adverse consequences on our business, such as:

•: requiring us to use a substantial portion of our cash flow from operations to service our indebtedness, which would reduce the available cash flow to fund working capital, capital expenditures, development projects and other general corporate purposes such as dividends;
•: limiting our ability to obtain additional financing to fund our working capital needs, acquisitions, capital expenditures or other debt service requirements or for other purposes;
•: limiting our ability to compete with other companies that are not as highly leveraged, as we may be less capable of responding to adverse economic and industry conditions;
•: restricting us from making other strategic acquisitions, developing additional properties or exploiting other business opportunities;
•: restricting the way in which we conduct our business because of financial and operating covenants in the agreements governing our and our subsidiaries' existing and future indebtedness;
•: exposing us to potential events of default (if not cured or waived) under financial and operating covenants contained in our or our subsidiaries' debt instruments that could have an adverse effect on our business, financial condition and operating results;
•: increasing our vulnerability to a downturn in general economic conditions; and
•: limiting our ability to react to changing market conditions in our industry.

In addition to our debt service obligations, our operations may require substantial investments on a continuing basis. Our ability to make scheduled debt payments, to refinance our obligations with respect to our indebtedness and to fund capital and non-capital expenditures necessary to maintain the condition of our operating assets and properties, as well as to provide capacity for the growth of our business, depends on our financial and operating performance, which, in turn, is subject to prevailing economic conditions and financial, business, competitive, legal and other factors.

We assumed substantially all liabilities related to the Archstone portfolio, and may be responsible for liabilities that were not known when we completed the Archstone Portfolio Acquisition.

Under the Purchase Agreement, we and Equity Residential assumed substantially all liabilities related to the Archstone portfolio, whether or not they were known by us, Equity Residential or LBHI at the time we entered into the Purchase Agreement, and we have agreed to indemnify LBHI with respect to these liabilities. Under the Purchase Agreement, we would be solely liable for these obligations if Equity Residential were to default on its obligation to share these indemnification obligations with us. As a result, we could become liable for liabilities that are not currently known to us, and the amount of these liabilities could have an adverse effect on our business, financial condition and results of operations.

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We intend to dispose of certain assets acquired in connection with the Archstone Portfolio Acquisition, but we may be unable to achieve the expected proceeds of these acquisitions or may be unable to dispose of these assets at all.

We intend to dispose of certain assets acquired in connection with the Archstone Portfolio Acquisition, including assets held in our joint ventures with Equity Residential, but we cannot predict whether we will be able to sell any of the properties on favorable terms and conditions, if at all, or the length of time over which we expect to sell any of the assets. We may be unable to sell some of the properties, which may adversely affect our liquidity, or we may have to sell properties at depressed prices, which could adversely affect our results of operations and financial condition. Our joint ventures with Equity Residential will own, among other assets, investments in apartment communities in Germany, and we acquired from Jupiter interests in U.S. markets that we are not currently in, including Florida, Georgia and Texas. Our efforts to manage, position and/or dispose of these investments may distract management and we may not achieve the intended results.

Future sales or issuances of our common stock may cause the market price of our common stock to decline.

In connection with the Archstone Portfolio Acquisition, we issued 14,889,706 shares of our common stock under the Purchase Agreement, and we have filed this Registration Statement to register the resale of these shares of common stock under the Securities Act. Any sale of substantial amounts of our common stock (whether directly by us or by existing stockholders in the secondary market), the perception that such sales could occur, or the availability for future sale of shares of our common stock or securities convertible into or exchangeable or exercisable for our common stock, could adversely affect the market price of our common stock and our ability to raise capital through future offerings of equity or equity-related securities.

Development, redevelopment and construction risks could affect our profitability.

We intend to continue to develop and redevelop apartment home communities. These activities can include long planning and entitlement timelines and can involve complex and costly activities, including significant environmental remediation or construction work in high-density urban areas. These activities may be exposed to the following risks:

•: we may abandon opportunities that we have already begun to explore for a number of reasons, including changes in local market conditions or increases in construction or financing costs, and, as a result, we may fail to recover expenses already incurred in exploring those opportunities;
•: occupancy rates and rents at a community may fail to meet our original expectations for a number of reasons, including changes in market and economic conditions beyond our control and the development by competitors of competing communities;
•: we may be unable to obtain, or experience delays in obtaining, necessary zoning, occupancy, or other required governmental or third party permits and authorizations, which could result in increased costs or the delay or abandonment of opportunities;
•: we may incur costs that exceed our original estimates due to increased material, labor or other costs;
•: we may be unable to complete construction and lease-up of a community on schedule, resulting in increased construction and financing costs and a decrease in expected rental revenues;
•: we may be unable to obtain financing with favorable terms, or at all, for the proposed development of a community, which may cause us to delay or abandon an opportunity;
•: we may incur liabilities to third parties during the development process, for example, in connection with managing existing improvements on the site prior to tenant terminations and

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demolition (such as commercial space) or in connection with providing services to third parties (such as the construction of shared infrastructure or other improvements); and

•: we may incur liability if our communities are not constructed and operated in compliance with the accessibility provisions of the Americans with Disabilities Acts, the Fair Housing Act or other federal, state or local requirements. Noncompliance could result in imposition of fines, an award of damages to private litigants, and a requirement that we undertake structural modifications to remedy the noncompliance.

We estimate construction costs based on market conditions at the time we prepare our budgets, and our projections include changes that we anticipate but cannot predict with certainty. Construction costs may increase, particularly for labor and certain materials and, for some of our Development Communities and Development Rights (as we use those terms in our quarterly and annual reports filed with the SEC), the total construction costs may be higher than the original budget. Total capitalized cost includes all capitalized costs incurred and projected to be incurred to develop or redevelop a community, determined in accordance with United States Generally Accepted Accounting Principles, or GAAP, including:

•: land and/or property acquisition costs;
•: fees paid to secure air rights and/or tax abatements;
•: construction or reconstruction costs;
•: costs of environmental remediation;
•: real estate taxes;
•: capitalized interest and insurance;
•: loan fees;
•: permits;
•: professional fees;
•: allocated development or redevelopment overhead; and
•: other regulatory fees.

Costs to redevelop communities that have been acquired have, in some cases, exceeded our original estimates and similar increases in costs may be experienced in the future. We cannot assure you that market rents in effect at the time new development or redevelopment communities complete lease-up will be sufficient to fully offset the effects of any increased construction or reconstruction costs.

Unfavorable changes in market and economic conditions could adversely affect occupancy, rental rates, operating expenses, and the overall market value of our assets, including joint ventures and investments in the Funds.

Local conditions in our markets significantly affect occupancy, rental rates and the operating performance of our communities. The risks that may adversely affect conditions in those markets include the following:

•: plant closings, industry slowdowns and other factors that adversely affect the local economy;
•: an oversupply of, or a reduced demand for, apartment homes;
•: a decline in household formation or employment or lack of employment growth;

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•: the inability or unwillingness of residents to pay rent increases;
•: rent control or rent stabilization laws, or other laws regulating housing, that could prevent us from raising rents to offset increases in operating costs; and
•: economic conditions that could cause an increase in our operating expenses, such as increases in property taxes, utilities, compensation of on-site associates and routine maintenance.

Changes in applicable laws, or noncompliance with applicable laws, could adversely affect our operations or expose us to liability.

We must develop, construct and operate our communities in compliance with numerous federal, state and local laws and regulations, some of which may conflict with one another or be subject to limited judicial or regulatory interpretations. These laws and regulations may include zoning laws, building codes, landlord tenant laws and other laws generally applicable to business operations. Noncompliance with laws could expose us to liability.

Lower revenue growth or significant unanticipated expenditures may result from our need to comply with changes in (i) laws imposing remediation requirements and the potential liability for environmental conditions existing on properties or the restrictions on discharges or other conditions, (ii) rent control or rent stabilization laws or other residential landlord/tenant laws, or (iii) other governmental rules and regulations or enforcement policies affecting the development, use and operation of our communities, including changes to building codes and fire and life-safety codes.

Short-term leases expose us to the effects of declining market rents.

Substantially all of our apartment leases are for a term of one year or less. Because these leases generally permit the residents to leave at the end of the lease term without penalty, our rental revenues are impacted by declines in market rents more quickly than if our leases were for longer terms.

Competition could limit our ability to lease apartment homes or increase or maintain rents.

Our apartment communities compete with other housing alternatives to attract residents, including other rental apartments, condominiums and single-family homes that are available for rent, as well as new and existing condominiums and single-family homes for sale. Competitive residential housing in a particular area could adversely affect our ability to lease apartment homes and to increase or maintain rental rates.

Attractive investment opportunities may not be available, which could adversely affect our profitability.

We expect that other real estate investors, including insurance companies, pension funds, other real estate investment trusts, or REITs, and other well-capitalized investors, will compete with us to acquire existing properties and to develop new properties. This competition could increase prices for properties of the type we would likely pursue and adversely affect our profitability.

Capital and credit market conditions may adversely affect our access to various sources of capital and/or the cost of capital, which could impact our business activities, dividends, earnings, and common stock price, among other things.

In periods when the capital and credit markets experience significant volatility, the amounts, sources and cost of capital available to us may be adversely affected. We primarily use external financing to fund construction and to refinance indebtedness as it matures. If sufficient sources of external financing are not available to us on cost effective terms, we could be forced to limit our development and redevelopment activity and/or take other actions to fund our business activities and repayment of debt, such as selling assets, reducing our cash dividend or paying out less than 100% of

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our taxable income. To the extent that we are able and/or choose to access capital at a higher cost than we have experienced in recent years (reflected in higher interest rates for debt financing or a lower stock price for equity financing) our earnings per share and cash flows could be adversely affected. In addition, the price of our common stock may fluctuate significantly and/or decline in a high interest rate or volatile economic environment. We believe that the lenders under our unsecured credit facility will fulfill their lending obligations thereunder, but if economic conditions deteriorate, there can be no assurance that the ability of those lenders to fulfill their obligations would not be adversely impacted.

Insufficient cash flow could affect our debt financing and create refinancing risk.

We are subject to the risks associated with debt financing, including the risk that our cash flow will be insufficient to meet required payments of principal and interest. In this regard, we note that in order for us to continue to qualify as a REIT, we are required to annually distribute dividends generally equal to at least 90% of our REIT taxable income, computed without regard to the dividends paid deduction and our net capital gain. This requirement limits the amount of our cash flow available to meet required principal and interest payments. The principal outstanding balance on a portion of our debt will not be fully amortized prior to its maturity. Although we may be able to repay our debt by using our cash flows, we cannot assure you that we will have sufficient cash flows available to make all required principal payments. Therefore, we may need to refinance at least a portion of our outstanding debt as it matures. There is a risk that we may not be able to refinance existing debt or that a refinancing will not be done on as favorable terms; either of these outcomes could have a material adverse effect on our financial condition and results of operations.

Rising interest rates could increase interest costs and could affect the market price of our common stock.

We currently have, and may in the future incur, contractual variable interest rate debt. In addition, we regularly seek access to both fixed and variable rate debt financing to repay maturing debt and to finance our development and redevelopment activity. Accordingly, if interest rates increase, our interest costs will also rise, unless we have made arrangements that hedge the risk of rising interest rates. In addition, an increase in market interest rates may lead purchasers of our common stock to demand a greater annual dividend yield, which could adversely affect the market price of our common stock.

Bond financing and zoning compliance requirements could limit our income, restrict the use of communities and cause favorable financing to become unavailable.

We have financed some of our apartment communities with obligations issued by local government agencies because the interest paid to the holders of this debt is generally exempt from federal income taxes and, therefore, the interest rate is generally more favorable to us. These obligations are commonly referred to as "tax-exempt bonds" and generally must be secured by mortgages on our communities. As a condition to obtaining tax-exempt financing, or on occasion as a condition to obtaining favorable zoning in some jurisdictions, we will commit to make some of the apartments in a community available to households whose income does not exceed certain thresholds (e.g., 50% or 80% of area median income), or who meet other qualifying tests. As of December 31, 2012, approximately 6.47% of our apartment homes at current operating communities were under income limitations such as these. These commitments, which may run without expiration or may expire after a period of time (such as 15 or 20 years) may limit our ability to raise rents and, in consequence, can also adversely affect the value of the communities subject to these restrictions.

In addition, some of our tax-exempt bond financing documents require us to obtain a guarantee from a financial institution of payment of the principal of, and interest on, the bonds. The guarantee may take the form of a letter of credit, surety bond, guarantee agreement or other additional collateral. If the financial institution defaults in its guarantee obligations, or if we are unable to renew the

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applicable guarantee or otherwise post satisfactory collateral, a default will occur under the applicable tax-exempt bonds and the community could be foreclosed upon if we do not redeem the bonds.

Risks related to indebtedness.

We have a $1,300,000,000 revolving variable rate unsecured credit facility with Bank of America, N.A., as administrative agent, swing lender, issuing bank and a bank, JPMorgan Chase Bank, N.A., as a bank and as syndication agent, Deutsche Bank Trust Company Americas, Morgan Stanley Bank and Wells Fargo Bank, N.A., each as a bank and as documentation agent, Barclays Bank PLC as a bank and as co-documentation agent, UBS AG, Stamford Branch, as a co-documentation agent, Goldman Sachs Bank USA, The Bank of New York Mellon, Compass Bank, PNC Bank, National Association, and Suntrust Bank, each as a bank and as a managing agent, Branch Banking and Trust Company, Bank of Tokyo Mitsubishi UFJ, Ltd., and Capital One, N.A., each as a bank and as a co-agent, and the other bank parties signatory thereto. Our organizational documents do not limit the amount or percentage of indebtedness that may be incurred. Accordingly, subject to compliance with outstanding debt covenants, we could incur more debt, resulting in an increased risk of default on our obligations and an increase in debt service requirements that could adversely affect our financial condition and results of operations.

The mortgages on those of our properties that are subject to secured debt, our unsecured credit facility and the indenture under which a substantial portion of our debt was issued contain customary restrictions, requirements and other limitations, as well as certain financial and operating covenants including maintenance of certain financial ratios. Maintaining compliance with these restrictions could limit our flexibility. A default in these requirements, if uncured, could result in a requirement that we repay indebtedness, which could severely affect our liquidity and increase our financing costs.

The mortgages on those of our properties subject to secured debt generally include provisions which stipulate a prepayment penalty or payment that we will be obligated to pay in the event that we elect to repay the mortgage note prior to the earlier of (i) the stated maturity of the note, or (ii) the date at which the mortgage note is prepayable without such penalty or payment. If we elect to repay some or all of the outstanding principal balance for our mortgage notes, we may incur prepayment penalties or payments under these provisions which could adversely affect our results of operations.

Debt financing may not be available and equity issuances could be dilutive to our stockholders.

Our ability to execute our business strategy depends on our access to an appropriate blend of debt and equity financing. Debt financing may not be available in sufficient amounts or on favorable terms. If we issue additional equity securities, the interests of existing stockholders could be diluted.

Failure to maintain our current credit ratings could adversely affect our cost of funds, related margins, liquidity and access to capital markets.

There are two major debt rating agencies that routinely evaluate and rate our debt. These ratings are based on a number of factors, which include their assessment of our financial strength, liquidity, capital structure, asset quality amount of real estate under development, and sustainability of cash flow and earnings, among other factors. If market conditions change, we may not be able to maintain our current credit ratings, which could adversely affect our cost of funds and related margins, liquidity, and access to capital markets.

We could be negatively impacted by the condition of Fannie Mae or Freddie Mac.

Fannie Mae and Freddie Mac are a major source of secured financing to the multifamily industry and we have used Fannie Mae and Freddie Mac for a portion of our financing needs. In February 2011, the Obama administration released a report calling for the winding down of the role that Fannie

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Mae and Freddie Mac play in the mortgage market. A final decision by the government to eliminate Fannie Mae or Freddie Mac or reduce their acquisitions or guarantees of multifamily community loans may adversely affect interest rates, capital availability, and the value of multifamily communities.

Failure to generate sufficient revenue or other liquidity needs could limit cash flow available for distributions to stockholders.

A decrease in rental revenue, or liquidity needs such as the repayment of indebtedness or funding of our development activities, could have an adverse effect on our ability to pay distributions to our stockholders. Significant expenditures associated with each community such as debt service payments, if any, real estate taxes, insurance and maintenance costs are generally not reduced when circumstances cause a reduction in income from a community.

The form, timing and/or amount of dividend distributions in future periods may vary and be impacted by economic and other considerations.

The form, timing and/or amount of dividend distributions will be declared at the discretion of the Board of Directors and will depend on actual cash from operations, our financial condition, capital requirements, the annual distribution requirements under the REIT provisions of the Internal Revenue Code of 1986, as amended, or the Internal Revenue Code or the Code, and other factors as the Board of Directors may consider relevant. The Board of Directors may modify our dividend policy from time to time.

We may choose to pay dividends in our own stock, in which case stockholders may be required to pay tax in excess of the cash they receive.

We may distribute taxable dividends that are payable in part in our stock, as we did in the fourth quarter of 2008. Taxable stockholders receiving such dividends will be required to include the full amount of the dividend as income to the extent of our current and accumulated earnings and profits for federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of the cash received. If a U.S. stockholder sells the stock it receives as a dividend in order to pay this tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, the trading price of our stock would experience downward pressure if a significant number of our stockholders sell shares of our stock in order to pay taxes owed on dividends.

Difficulty of selling apartment communities could limit liquidity and financial flexibility.

Federal tax laws may limit our ability to earn a gain on the sale of a community (unless we own it through a subsidiary which will incur a taxable gain upon sale) if we are found to have held, acquired or developed the community primarily with the intent to resell the community, and this limitation may affect our ability to sell communities without adversely affecting returns to our stockholders. In addition, real estate in our markets can at times be difficult to sell quickly at prices we find acceptable. These potential difficulties in selling real estate in our markets may limit our ability to change or reduce the apartment communities in our portfolio promptly in response to changes in economic or other conditions.

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Acquisitions may not yield anticipated results.

Our business strategy includes acquiring as well as developing communities. Our acquisition activities and their success may be exposed to the following risks:

•: an acquired property may fail to perform as we expected in analyzing our investment; and
•: our estimate of the costs of repositioning or redeveloping an acquired property may prove inaccurate.

Failure to succeed in new markets, or with new brands and community formats, or in activities other than the development, ownership and operation of residential rental communities may have adverse consequences.

We may from time to time commence development activity or make acquisitions outside of our existing market areas if appropriate opportunities arise. Our historical experience in our existing markets in developing, owning and operating rental communities does not ensure that we will be able to operate successfully in new markets, should we choose to enter them. We may be exposed to a variety of risks if we choose to enter new markets, including an inability to accurately evaluate local apartment market conditions; an inability to obtain land for development or to identify appropriate acquisition opportunities; an inability to hire and retain key personnel; and lack of familiarity with local governmental and permitting procedures.

Although we are primarily in the multifamily business, we also own and lease ancillary retail space when a retail component represents the best use of the space, as is often the case with large urban in-fill developments. We also may engage or have an interest in for-sale activity. We may be unsuccessful in owning and leasing retail space at our communities or in developing real estate with the intent to sell, which could have an adverse effect on our results of operations.

We are currently implementing two new brands of communities that target various customer preferences. We cannot assure that these brands will be successful or that our costs in developing and implementing these brands will result in incremental revenue and earnings.

Land we hold with no current intent to develop may be subject to future impairment charges.

We own parcels of land that we do not currently intend to develop. In the event that the fair market value of a parcel changes such that we determine that the carrying basis of the parcel reflected in our financial statements is greater than the parcel's then current fair value, less costs to dispose, we would be subject to an impairment charge, which would reduce our net income.

Risks involved in real estate activity through joint ventures.

Instead of acquiring or developing apartment communities directly, at times we invest as a partner or a co-venturer. Joint venture investments (including investments through partnerships or limited liability companies) involve risks, including the possibility that our partner might become insolvent or otherwise refuse to make capital contributions when due; that we may be responsible to our partner for indemnifiable losses; that our partner might at any time have business goals which are inconsistent with ours; and that our partner may be in a position to take action or withhold consent contrary to our instructions or requests. Frequently, we and our partner may each have the right to trigger a buy-sell arrangement, which could cause us to sell our interest, or acquire our partner's interest, at a time when we otherwise would not have initiated such a transaction.

Risks associated with an investment in and management of discretionary real estate investment funds.

We formed our two discretionary institutional real estate investment funds, or the Funds, in which we have an equity interest of 15.2% and 31.3%, respectively, which, through wholly-owned subsidiaries,

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we manage as the general partner and in which we have an aggregate equity investment, excluding costs incurred in excess of our equity in the underlying net assets of each respective fund, of approximately $129,059,000, net of distributions to us at December 31, 2012. The investment period for both Funds is over. These Funds present risks, including the following:

•: our subsidiaries that are the general partners of the Funds are generally liable, under partnership law, for the debts and obligations of the respective Funds, subject to certain exculpation and indemnification rights pursuant to the terms of the partnership agreement of the Funds;
•: investors in the Funds holding a majority of the partnership interests may remove us as the general partner without cause, subject to our right to receive an additional nine months of management fees after such removal and our right to acquire one of the properties then held by the Funds;
•: while we have broad discretion to manage the Funds and make investment decisions on behalf of the Funds, the investors or an advisory committee comprised of representatives of the investors must approve certain matters, and as a result we may be unable to cause the Funds to implement certain decisions that we consider beneficial; and
•: we may be liable and/or our status as a REIT may be jeopardized if either the Funds, or the REITs through which a number of investors have invested in the Funds and which we manage, fail to comply with various tax or other regulatory matters.

Risk of earthquake damage.

Many of our West Coast communities are located in the general vicinity of active earthquake faults. We cannot assure you that an earthquake would not cause damage or losses greater than insured levels. In the event of a loss in excess of insured limits, we could lose our capital invested in the affected community, as well as anticipated future revenue from that community. We would also continue to be obligated to repay any mortgage indebtedness or other obligations related to the community. Any such loss could materially and adversely affect our business and our financial condition and results of operations.

Insurance coverage for earthquakes can be costly due to limited industry capacity. As a result, we may experience shortages in desired coverage levels if market conditions are such that insurance is not available or the cost of insurance makes it, in management's view, economically impractical.

A significant uninsured property or liability loss could have a material adverse effect on our financial condition and results of operations.

In addition to the earthquake insurance discussed above, we carry commercial general liability insurance, property insurance and terrorism insurance with respect to our communities on terms we consider commercially reasonable. There are, however, certain types of losses (such as losses arising from acts of war) that are not insured, in full or in part, because they are either uninsurable or the cost of insurance makes it, in management's view, economically impractical. If an uninsured property loss or a property loss in excess of insured limits were to occur, we could lose our capital invested in a community, as well as the anticipated future revenues from such community. We would also continue to be obligated to repay any mortgage indebtedness or other obligations related to the community. If an uninsured liability to a third party were to occur, we would incur the cost of defense and settlement with, or court ordered damages to, that third party. A significant uninsured property or liability loss could materially and adversely affect our business and our financial condition and results of operations.

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We may incur costs and increased expenses to repair property damage resulting from inclement weather.

Particularly in New England and the Metro New York/New Jersey area, we are exposed to risks associated with inclement winter weather, including increased costs for the removal of snow and ice, repair of water and wind damage from storms, as well as from delays in construction. In addition, inclement weather could increase the need for maintenance and repair of our communities.

We may incur costs due to environmental contamination or non-compliance.

Under various federal, state and local environmental and public health laws, regulations and ordinances, we may be required, regardless of knowledge or responsibility, to investigate and remediate the effects of hazardous or toxic substances or petroleum product releases at our properties (including in some cases natural substances such as methane and radon gas) and may be held liable under these laws or common law to a governmental entity or to third parties for property, personal injury or natural resources damages and for investigation and remediation costs incurred as a result of the contamination. These damages and costs may be substantial and may exceed any insurance coverage we have for such events. The presence of such substances, or the failure to properly remediate the contamination, may adversely affect our ability to borrow against, develop, sell or rent the affected property.

In addition, some environmental laws create or allow a government agency to impose a lien on the contaminated site in favor of the government for damages and costs it incurs as a result of the contamination.

The development, construction and operation of our communities are subject to regulations and permitting under various federal, state and local laws, regulations and ordinances, which regulate matters including wetlands protection, storm water runoff and wastewater discharge. Such laws and regulations may impose restrictions on the manner in which our communities may be developed, and noncompliance with such laws and regulations may subject us to fines and penalties. We do not currently anticipate that we will incur any material liabilities as a result of noncompliance with these laws.

Certain federal, state and local laws, regulations and ordinances govern the removal, encapsulation or disturbance of asbestos containing materials ("ACMs") when such materials are in poor condition or in the event of renovation or demolition of a building. These laws and the common law may impose liability for release of ACMs and may allow third parties to seek recovery from owners or operators of real properties for personal injury associated with exposure to ACMs. We are not aware that any ACMs were used in the construction of the communities we developed. ACMs were, however, used in the construction of a number of the communities that we acquired. We implement an operations and maintenance program at each of the communities at which ACMs are detected. We do not currently anticipate that we will incur any material liabilities as a result of the presence of ACMs at our communities.

We are aware that some of our communities have lead paint and have implemented an operations and maintenance program at each of those communities. We do not currently anticipate that we will incur any material liabilities as a result of the presence of lead paint at our communities.

Environmental agencies and third parties may assert claims for remediation or personal injury based on the alleged actual or potential intrusion into buildings of chemical vapors from soils or groundwater underlying or in the vicinity of those buildings or on nearby properties. We currently do not anticipate that we will incur any material liabilities as a result of vapor intrusion at our communities.

All of our stabilized operating communities, and all of the communities that we are currently developing, have been subjected to at least a Phase I or similar environmental assessment, which

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generally does not involve invasive techniques such as soil or ground water sampling. These assessments, together with subsurface assessments conducted on some properties, have not revealed, and we are not otherwise aware of, any environmental conditions that we believe would have a material adverse effect on our business, assets, financial condition or results of operations. In connection with our ownership, operation and development of communities, from time to time we undertake substantial remedial action in response to the presence of subsurface or other contaminants, including contaminants in soil, groundwater and soil vapor beneath or affecting our buildings. In some cases, an indemnity exists upon which we may be able to rely if environmental liability arises from the contamination or remediation costs exceed estimates. There can be no assurance, however, that all necessary remediation actions have been or will be undertaken at our properties or that we will be indemnified, in full or at all, in the event that environmental liability arises.

Mold growth may occur when excessive moisture accumulates in buildings or on building materials, particularly if the moisture problem remains undiscovered or is not addressed over a period of time. Although the occurrence of mold at multifamily and other structures, and the need to remediate such mold, is not a new phenomenon, there has been increased awareness in recent years that certain molds may in some instances lead to adverse health effects, including allergic or other reactions. To help limit mold growth, we educate residents about the importance of adequate ventilation and request or require that they notify us when they see mold or excessive moisture. We have established procedures for promptly addressing and remediating mold or excessive moisture from apartment homes when we become aware of its presence regardless of whether we or the resident believe a health risk is presented. However, we cannot provide assurance that mold or excessive moisture will be detected and remediated in a timely manner. If a significant mold problem arises at one of our communities, we could be required to undertake a costly remediation program to contain or remove the mold from the affected community and could be exposed to other liabilities that may exceed any applicable insurance coverage.

Additionally, we have occasionally been involved in developing, managing, leasing and operating various properties for third parties. Consequently, we may be considered to have been an operator of such properties and, therefore, potentially liable for removal or remediation costs or other potential costs which relate to the release or presence of hazardous or toxic substances or petroleum products at such properties. We are not aware of any material environmental liabilities with respect to properties managed or developed by us or our predecessors for such third parties.

We cannot assure you that:

•: the environmental assessments described above have identified all potential environmental liabilities;
•: no prior owner created any material environmental condition not known to us or the consultants who prepared the assessments;
•: no environmental liabilities have developed since the environmental assessments were prepared;
•: the condition of land or operations in the vicinity of our communities, such as the presence of underground storage tanks, will not affect the environmental condition of our communities;
•: future uses or conditions, including, without limitation, changes in applicable environmental laws and regulations, will not result in the imposition of environmental liability; and
•: no environmental liabilities will arise at communities that we have sold for which we may have liability.

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Our success depends on key personnel whose continued service is not guaranteed.

Our success depends in part on our ability to attract and retain the services of executive officers and other personnel. Our executive officers make important capital allocation decisions or recommendations to our Board of Directors from among the opportunities identified by our regional offices. There is substantial competition for qualified personnel in the real estate industry, and the loss of several of our key personnel could adversely affect the Company.

Breaches of our data security could materially harm our business and reputation.

We collect and retain certain personal information provided by our residents and employees. While we have implemented a variety of security measures to protect the confidentiality of this information and periodically review and improve our security measures, there can be no assurance that we will be able to prevent unauthorized access to this information. Any breach of our data security measures and loss of this information may result in legal liability and costs (including damages and penalties), as well as damage to our reputation, that could materially and adversely affect our business and financial performance.

Failure to qualify as a REIT would cause us to be taxed as a corporation, which would significantly reduce funds available for distribution to stockholders.

If we fail to qualify as a REIT for federal income tax purposes, we will be subject to federal income tax on our taxable income at regular corporate rates (subject to any applicable alternative minimum tax). In addition, unless we are entitled to relief under applicable statutory provisions, we would be ineligible to make an election for treatment as a REIT for the four taxable years following the year in which we lose our qualification. The additional tax liability resulting from the failure to qualify as a REIT would significantly reduce or eliminate the amount of funds available for distribution to our stockholders. Furthermore, we would no longer be required to make distributions to our stockholders. Thus, our failure to qualify as a REIT could also impair our ability to expand our business and raise capital, and would adversely affect the value of our common stock.

We believe that we are organized and qualified as a REIT, and we intend to operate in a manner that will allow us to continue to qualify as a REIT. However, we cannot assure you that we are qualified as a REIT, or that we will remain qualified in the future. This is because qualification as a REIT involves the application of highly technical and complex provisions of the Internal Revenue Code for which there are only limited judicial and administrative interpretations and involves the determination of a variety of factual matters and circumstances not entirely within our control. In addition, future legislation, new regulations, administrative interpretations or court decisions may significantly change the tax laws or the application of the tax laws with respect to qualification as a REIT for federal income tax purposes or the federal income tax consequences of this qualification.

The Archstone Portfolio Acquisition presents additional risks to our qualification as a REIT. Although we believe we have structured our ownership of the assets and entities acquired in connection with the Archstone Portfolio Acquisition, and will be able to operate such assets and entities, in a way that will allow us to continue to qualify as a REIT for federal income tax purposes, no assurances can be given that we will be successful. Our tax diligence investigations with respect to the assets and entities comprising the Archstone Portfolio Acquisition were more limited than would be the case if we were acquiring individual properties, and our on-going review may reveal non-qualifying assets or income not previously accounted for. Among the assets included in the Archstone Portfolio Acquisition are subsidiaries intended to qualify as REITs. Our REIT qualification could depend in part on such subsidiaries' compliance with the REIT requirements before our purchase.

The assets of one of our joint ventures with Equity Residential include indirect interests in partnerships controlled by Equity Residential. For purposes of our compliance with the REIT asset and

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gross income requirements, we will be treated as owning our proportionate share of the assets of the Equity Residential partnerships in which the joint venture has an interest. Although Equity Residential has agreed to operate those partnerships in compliance with the REIT requirements, we cannot assure you that such Equity Residential partnerships will be operated in compliance with the REIT requirements. Failure by those partnerships to comply with the REIT requirements could potentially jeopardize our REIT status.

Even if we qualify as a REIT, we will be subject to certain federal, state and local taxes on our income and property and on taxable income that we do not distribute to our shareholders. Our non-U.S. assets may be subject to foreign taxes. In addition, we may hold certain assets and engage in certain activities that a REIT could not engage in directly through our taxable REIT subsidiaries. We also use taxable REIT subsidiaries to hold certain assets that we believe would be subject to the 100% prohibited transaction tax if sold at a gain outside of a taxable REIT subsidiary. Our domestic taxable REIT subsidiaries are subject to U.S. tax as regular corporations. The Archstone Portfolio Acquisition increased the amount of assets held through our taxable REIT subsidiaries.

The ability of our stockholders to control our policies and effect a change of control of our company is limited by certain provisions of our charter and bylaws and by Maryland law.

There are provisions in our charter and bylaws that may discourage a third party from making a proposal to acquire us, even if some of our stockholders might consider the proposal to be in their best interests. These provisions include the following:

Our charter authorizes our Board of Directors to issue up to 50,000,000 shares of preferred stock without stockholder approval and to establish the preferences and rights, including voting rights, of any series of preferred stock issued. The Board of Directors may issue preferred stock without stockholder approval, which could allow the Board to issue one or more classes or series of preferred stock that could discourage or delay a tender offer or a change in control.

To maintain our qualification as a REIT for federal income tax purposes, not more than 50% in value of our outstanding stock may be owned, directly or indirectly, by or for five or fewer individuals at any time during the last half of any taxable year. To maintain this qualification, and/or to address other concerns about concentrations of ownership of our stock, our charter generally prohibits ownership (directly, indirectly by virtue of the attribution provisions of the Code, or beneficially as defined in Section 13 of the Securities Exchange Act of 1934, or the Exchange Act) by any single stockholder of more than 9.8% of the issued and outstanding shares of any class or series of our stock. In general, under our charter, pension plans and mutual funds may directly and beneficially own up to 15% of the outstanding shares of any class or series of stock. Under our charter, our Board of Directors may in its sole discretion waive or modify the ownership limit for one or more persons, but is not required to do so even if such waiver would not affect our qualification as a REIT. These ownership limits may prevent or delay a change in control and, as a result, could adversely affect our stockholders' ability to realize a premium for their shares of common stock. Prior to the issuance of the shares of common stock in connection with the Archstone Portfolio Acquisition, our Board of Directors waived this ownership limit with respect to ownership of such shares by LBHI, Jupiter Enterprise LP (formerly known as Archstone Enterprise LP) and certain of their subsidiaries and affiliates as provided in a Waiver of Ownership Limit dated as of November 26, 2012 addressed to LBHI.

As a Maryland corporation, we are subject to the provisions of the Maryland General Corporation Law. Maryland law imposes restrictions on some business combinations and requires compliance with statutory procedures before some mergers and acquisitions may occur, which may delay or prevent offers to acquire us or increase the difficulty of completing any offers, even if they are in our stockholders' best interests. In addition, other provisions of the Maryland General Corporation Law permit the Board of Directors to make elections and to take actions without stockholder approval (such as classifying our Board such that the entire Board is not up for re-election annually) that, if made or taken, could have the effect of discouraging or delaying a change in control.

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Forward-Looking Statements

This prospectus and any prospectus supplement, including the information incorporated by reference therein, contain statements that are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, or the Securities Act, and Section 21E of the Exchange Act. You can identify forward-looking statements by the use of the words "believe," "expect," "anticipate," "intend," "estimate," "assume," "plan," "project," "may," "shall," "will," "outlook" and other similar expressions that predict or indicate future events and trends and which do not relate to historical matters. These statements include, among other things, statements regarding our intent, belief or expectations with respect to:

•: our potential development, redevelopment, acquisition or disposition of communities;
•: the timing and cost of completion of apartment communities under construction, reconstruction, development or redevelopment;
•: the timing of lease-up, occupancy and stabilization of apartment communities;
•: the pursuit of land on which we are considering future development;
•: the anticipated operating performance of our communities;
•: cost, yield, revenue, net operating income and earnings estimates;
•: our declaration or payment of distributions;
•: our joint venture and discretionary fund activities;
•: our policies regarding investments, indebtedness, acquisitions, dispositions, financings and other matters;
•: our qualification as a REIT under the Code;
•: the real estate markets in Northern and Southern California and markets in selected states in the Mid-Atlantic, New England, Metro New York/New Jersey and Pacific Northwest regions of the United States and in general;
•: the availability of debt and equity financing;
•: interest rates;
•: general economic conditions including potential impacts from the current economic conditions; and
•: trends affecting our financial condition or results of operations.

We cannot assure the future results or outcome of the matters described in these statements; rather, these statements merely reflect our current expectations of the approximate outcomes of the matters discussed. In addition, these forward-looking statements represent our estimates and assumptions only as of the date of this prospectus. We do not undertake a duty to update these forward-looking statements, and therefore they may not represent our estimates and assumptions after the date of this report. You should not rely on forward-looking statements because they involve known and unknown risks, uncertainties and other factors, some of which are beyond our control. These risks, uncertainties and other factors, some of which we describe in "Risk Factors elsewhere in this prospectus, may cause our actual results, performance or achievements to differ materially from the anticipated future results, performance or achievements expressed or implied by these forward-looking statements. In addition to the factors referred to below, you should carefully review the discussion under "Risk Factors" and the other disclosures elsewhere in this document for further discussion of additional risks and uncertainties associated with our business and these forward-looking statements.

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•: we may fail to secure development opportunities due to an inability to reach agreements with third parties to obtain land at attractive prices or to obtain desired zoning and other local approvals;
•: we may abandon or defer development opportunities for a number of reasons, including changes in local market conditions which make development less desirable, increases in costs of development, increases in the cost of capital or lack of capital availability, resulting in losses;
•: construction costs of a community may exceed our original estimates;
•: we may not complete construction and lease-up of communities under development or redevelopment on schedule, resulting in increased interest costs and construction costs and a decrease in our expected rental revenues;
•: occupancy rates and market rents may be adversely affected by competition and local economic and market conditions which are beyond our control;
•: financing may not be available on favorable terms or at all, and our cash flows from operations and access to cost effective capital may be insufficient for the development of our pipeline which could limit our pursuit of opportunities;
•: our cash flows may be insufficient to meet required payments of principal and interest, and we may be unable to refinance existing indebtedness or the terms of such refinancing may not be as favorable as the terms of existing indebtedness;
•: we may be unsuccessful in our management of Fund I, Fund II or the REIT vehicles that are used with each respective Fund; and
•: we may be unsuccessful in managing changes in our portfolio composition.

In addition, any forward-looking statements or forecasts relating to the business, prospects, operating statistics or financial results that relate to or may be expected to result from the Archstone Portfolio Acquisition are based on expectations, forecasts and assumptions that are inherently speculative and are subject to substantial risks and uncertainties, many of which we cannot predict with accuracy and some of which we may not have anticipated. As a result, the actual operating statistics and financial results that relate to or may be expected to result from the Archstone Portfolio Acquisition may differ materially from the Company's forecasts. Risks, uncertainties and other factors related to the Archstone Portfolio Acquisition that might cause such differences include, among other things, the following: we may not be able to integrate the assets and operations acquired in the Archstone Portfolio Acquisition in a manner consistent with our assumptions and/or we may fail to achieve expected efficiencies and synergies; we may encounter liabilities related to the Archstone Portfolio Acquisition for which we may be responsible that were unknown to us at the time we agreed to the Archstone Portfolio Acquisition or at the time of this prospectus; and our assumptions concerning risks relating to our lack of control of joint ventures and our ability to successfully dispose of certain assets may not be realized.

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About AvalonBay Communities, Inc.

AvalonBay Communities, Inc. is a real estate investment trust, or REIT, and S&P 500 Index company that owns one of the largest portfolios of high-quality multifamily communities in the United States. We are focused on the development, redevelopment, acquisition, operation and management of apartment communities in high barrier-to-entry markets in the Northeast, Mid-Atlantic and West Coast regions of the United States.

At January 31, 2013, we owned or held a direct or indirect ownership interest in:

•: 178 operating apartment communities containing 52,427 apartment homes in nine states and the District of Columbia, of which 155 communities containing 45,056 apartment homes were consolidated for financial reporting purposes, two communities containing 674 apartment homes were held by joint ventures in which we hold an ownership interest, and 21 communities containing 6,697 apartment homes were owned by two institutional discretionary real estate investment funds which we manage and in which we hold ownership interests; five of the consolidated communities containing 1,787 apartment homes were under redevelopment at January 31, 2013;
•: 23 wholly-owned communities under construction that are expected to contain an aggregate of 6,599 apartment homes when completed; and
•: rights to develop an additional 34 communities that, if developed in the manner expected, will contain an estimated 9,602 apartment homes.

Our principal financial goal is to increase long-term stockholder value through the development, redevelopment, acquisition, operation, and when appropriate, disposition of apartments in our markets. To help meet this goal, we regularly (i) monitor our investment allocation by geographic market and product type, (ii) develop, redevelop and acquire an interest in apartment communities in high barrier to entry markets with growing or high potential for demand and high for-sale housing costs, (iii) selectively sell apartment communities that no longer meet our long-term strategy or when opportunities are presented to realize a portion of the value created through our investment and redeploy the proceeds from those sales and (iv) endeavor to maintain a capital structure that is aligned with our business risks with a view to maintaining continuous access to cost-effective capital. Our strategy is to be leaders in multifamily market research, consumer insight and capital allocation, delivering a range of multifamily offerings tailored to serve the needs of the most attractive customer segments in the best-performing U.S. submarkets. A substantial majority of our current communities are upscale, which generally command among the highest rents in their markets. However, we also pursue the ownership and operation of apartment communities that target a variety of customer segments and price points, consistent with our goal of offering a broad range of products and services.

We operate our apartment communities under three core brandsAvalon, AVA, andEaves by Avalon. We believe that this branding differentiation allows us to target our product offerings to multiple customer groups and submarkets within our existing geographic footprint. The"Avalon" brand is our core offering, focusing on upscale apartment living and high end amenities and services in urban and suburban markets. Our"AVA" brand is designed for people who want to live in or near urban neighborhoods and in close proximity to public transportation, services, shopping and night-life.AVA apartments are generally smaller, many engineered for roommate living, and feature modern design and a technology focus. OurEaves by Avalon brand is designed for renters who seek good quality apartment living, often in a suburban setting, with practical amenities and services at a more modest price point.

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on our net income to the extent net income is distributed to our stockholders. We have historically made sufficient distributions to avoid tax on retained income, and we intend to make sufficient distributions to avoid income tax at the corporate level. While we believe that we are organized and qualified as a REIT and we intend to operate in a manner that will allow us to continue to qualify as a REIT, there can be no assurance that we will be successful in this regard. Qualification as a REIT involves the application of highly technical and complex provisions of the Internal Revenue Code of 1986, as amended, or the Code, for which there are limited judicial and administrative interpretations and involves the determination of a variety of factual matters and circumstances not entirely within our control.

Our principal executive offices are located at Ballston Tower, 671 N. Glebe Road, Suite 800, Arlington, Virginia 22203, Attention: Chief Financial Officer. Our telephone number is 703-329-6300. Our website is located at www.avalonbay.com. Information on our website is not deemed to be a part of this prospectus supplement or the attached prospectus. Our common stock is listed on the NYSE under the symbol "AVB."

The Archstone Portfolio Acquisition

On February 27, 2013, we completed the acquisition (the "Archstone Portfolio Acquisition") of certain assets that comprise approximately 40% of the assets of Archstone Enterprise LP, which subsequently changed its name to Jupiter Enterprise LP in accordance with the terms of the Purchase Agreement ("Jupiter"), with the remaining approximately 60% being acquired by Equity Residential, pursuant to a purchase and sale agreement (the "Purchase Agreement) dated November 26, 2012 among us, Equity Residential, Jupiter and LBHI. In connection with the Archstone Portfolio Acquisition, we issued the 14,889,706 shares of our common stock registered hereby; paid approximately $667 million in cash; assumed indebtedness with a fair value of approximately $4.0 billion; acquired (with Equity Residential) interests in entities that have preferred units outstanding that may be presented for redemption from time to time, of which our 40% share of the liquidation value of and accrued dividends on these outstanding Jupiter preferred units as of February 27, 2013 was approximately $70 million; and assumed (with Equity Residential) all other liabilities, known or unknown, of Jupiter, other than certain excluded liabilities, of which our share will be 40% of the cost of these liabilities. The Archstone Portfolio Acquisition is described in greater detail in our Annual Report on Form 10-K for the year ended December 31, 2012 and our Current Report on Form 8-K filed on March 5, 2013, which are incorporated herein by reference.

About This Offering

The securities offered in this prospectus relate to the potential resale of 14,889,706 shares of our common stock. The 14,889,706 shares of common stock were issued to Jupiter in connection with the Archstone Portfolio Acquisition. In connection with the Archstone Portfolio Acquisition, we agreed to file this registration statement to register the resale of the shares of our common stock issued to Jupiter. See "Plan of Distribution" for additional information concerning this registration statement.

Use of Proceeds

This prospectus relates to the securities that may be offered and sold from time to time by the selling stockholders who will receive all of the proceeds from any sale of the securities. We will not receive any of the proceeds from any sales of the securities by the selling stockholders. However, we will pay the registration expenses, including filing fees, printing fees and fees of our counsel and other advisers.

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Selling Stockholders

When we refer to the "selling stockholders" in this prospectus we mean the stockholder listed in the table below and its pledgees, donees, transferees or other successors in interest. The selling stockholders may from time to time offer and sell any or all of the shares of common stock set forth below pursuant to this prospectus. The selling stockholder listed in the table below acquired such shares of our common stock in connection with the Archstone Portfolio Acquisition. See "About this Offering."

Upon closing of the Archstone Portfolio Acquisition, we entered into certain agreements, including:

•: a Registration Rights Agreement, dated as of February 27, 2013 (the "Registration Rights Agreement"), pursuant to which we agreed to, among other things, file with the SEC a registration statement on Form S-3 to register the resale by the selling stockholders of the shares of common stock and which also grants the selling stockholders and certain affiliates certain additional customary registration rights to cover resales of the shares of common stock; and
•: a Shareholders Agreement, dated as of February 27, 2013 (the "Shareholders Agreement"), which, among other things, restricts the selling stockholders and certain affiliates from transferring any of the shares of common stock until April 26, 2013, imposes conditions on certain transfers after April 26, 2013, grants us customary standstill protections, and imposes certain voting requirements on the Selling Shareholders and certain affiliates.

Other than as set forth above and except as described in this prospectus, the selling stockholder listed below does not have, nor within the past three years has had, any material relationship with us or any of our affiliates.

We do not know when or in what amounts the selling stockholders may offer securities for sale, if at all. It is possible that the selling stockholders will not sell any or all of the shares offered under this prospectus. Because the selling stockholders may offer all or some of the securities pursuant to this prospectus and because we have been advised that there are currently no agreements, arrangements or understanding with respect to the sale of any such securities, we cannot estimate the number of securities that will be held by the selling stockholders after the completion of this offering. Solely for purposes of the table below, we have assumed that the selling stockholder will sell all of the securities held by it and therefore would hold no securities following the offering and hold zero percentage of the securities following the offering.

Information about the selling stockholders and certain transferees may change over time. Any changed information will be set forth in supplements to this prospectus, if required

	Shares of Common Stock Beneficially Owned Prior to Offering						Shares of Common Stock Owned After the Offering

Selling Stockholder	Shares		Percent				Shares		Percent
Jupiter Enterprise LP(1)		14,889,706		11.5	%	14,889,706		—		0	%

(1): The 14,889,706 shares of common stock are directly owned by Jupiter. Jupiter is an indirect subsidiary of LBHI. Under SEC rules regarding beneficial ownership, LBHI may be deemed to have voting and investment power over the shares of common stock shown in the table above. Lehman Brothers Holdings Inc. Plan Trust (the "Plan Trust") is the sole stockholder of LBHI. Despite this ownership, the Plan Trust does not have any voting or investment discretion with respect to the shares of common stock shown in the table above.

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Plan of Distribution

The selling stockholders, or their pledgees, donees, transferees, or any of their successors in interest selling the securities received from a named selling stockholder as a gift, partnership distribution or other non-sale-related transfer after the date of this prospectus (all of whom may be selling stockholders), may sell the securities from time to time on any stock exchange or automated interdealer quotation system on which the securities are traded, in the over-the-counter market, in privately negotiated transactions or otherwise, at fixed prices that may be changed, at market prices prevailing at the time of sale, at prices related to prevailing market prices or at prices otherwise negotiated, beginning April 27, 2013 in accordance with the Shareholders Agreement. The selling stockholders may sell the securities by one or more of the following methods, without limitation:

•: block trades in which the broker or dealer so engaged will attempt to sell the securities as agent but may position and resell a portion of the block as principal to facilitate the transaction, or in crosses in which the same broker acts as agent on both sides;
•: purchases by a broker or dealer as principal and resale by the broker or dealer for its own account pursuant to this prospectus;
•: an exchange distribution in accordance with the rules of any stock exchange on which the securities are listed or any automated inter-dealer quotation system on which the securities are traded;
•: ordinary brokerage transactions and transactions in which the broker solicits purchases;
•: privately negotiated transactions;
•: short sales;
•: through the writing of options on the securities, swaps or other derivatives, whether or not the options or other such instruments are listed on an exchange or inter-dealer quotation system;
•: through the distribution of the securities by any selling stockholder to its partners, members, equityholders or creditors who may from time to time effect sales or other distributions of the securities;
•: one or more underwritten offerings on a firm commitment or best efforts basis or other purchases by underwriters, brokers, dealers, and agents who may receive compensation in the form of underwriting discounts, concessions or commissions from the selling stockholders and/or the purchasers of the securities for whom they may act as agent;
•: pledges of the securities as security for any loan or obligation, including pledges to brokers or dealers who may from time to time effect sales or other distributions of the securities;
•: sales in other ways not involving market makers or established trading markets, including direct sales to institutions or individual purchasers; and
•: any combination of the foregoing methods or by any other legally available means.

The selling stockholders may also transfer the securities by gift. We do not know of any current arrangements by the selling stockholders for the sale of any of the securities.

The selling stockholders may engage underwriters, brokers or dealers, and any underwriters, brokers or dealers may arrange for other underwriters, brokers or dealers to participate in effecting sales of the securities. These brokers, dealers or underwriters may act as principals, or as an agent of a selling stockholder. Broker-dealers may agree with a selling stockholder to sell a specified number of the securities at a stipulated price per security. If the broker-dealer is unable to sell securities acting as agent for a selling stockholder, it may purchase as principal any unsold securities at the stipulated

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price. Broker-dealers who acquire securities as principals may thereafter resell the securities from time to time in transactions in any stock exchange or automated interdealer quotation system on which the securities are then listed or in over-the-counter market, at prices and on terms then prevailing at the time of sale, at prices related to the then-current market price or in negotiated transactions. Broker-dealers may use block transactions and sales to and through broker-dealers, including transactions of the nature described above. The selling stockholders may also sell the securities in accordance with Rule 144 under the Securities Act, or in accordance with Section 4(1) of the Securities Act, rather than pursuant to this prospectus, regardless of whether the securities are covered by this prospectus.

From time to time, one or more of the selling stockholders may pledge, hypothecate or grant a security interest in some or all of the securities owned by them. The pledgees, secured parties or persons to whom the securities have been so pledged or hypothecated (or otherwise subject to a security interest) will, upon foreclosure in the event of default, be deemed to be selling stockholders. The plan of distribution for that selling stockholder's securities will otherwise remain unchanged. The selling stockholders (or their pledgees, donees, transferees or other successors in interest) also may transfer and donate the securities in other circumstances in which case the transferees, donees, pledgees or other successors in interest thereof will be the selling stockholders for purposes of this prospectus and, if required under the Securities Act, will be identified in a prospectus supplement.

In addition, selling stockholders may, from time to time, sell the securities short, and, in those instances, this prospectus may be delivered in connection with the short sales and the securities offered under this prospectus may be used to cover short sales.

To the extent required under the Securities Act, the aggregate amount of selling stockholders' securities being offered and the terms of the offering, the names of any agents, brokers, dealers or underwriters and any applicable commission with respect to a particular offer will be set forth in an accompanying prospectus supplement. Any underwriters, dealers, brokers or agents participating in the distribution of the securities may receive compensation in the form of underwriting discounts, concessions, commissions or fees from a selling stockholder and/or purchasers of selling stockholders' securities, for whom they may act (which compensation as to a particular broker-dealer might be in excess of customary commissions). The maximum commission or discount to be received by any member of the Financial Industry Regulatory Authority, Inc. (FINRA) or independent broker-dealer will not be greater than 8% of the initial gross proceeds received by the selling stockholders from the sale of any securities being registered pursuant to Rule 415 under the Securities Act.

The selling stockholders and any underwriters, brokers, dealers or agents that participate in the distribution of the securities may be deemed to be "underwriters" within the meaning of the Securities Act, and any discounts, concessions, commissions or fees received by them and any profit on the resale of the securities sold by them may be deemed to be underwriting discounts and commissions.

The selling stockholders may enter into hedging transactions with broker-dealers and the broker-dealers may engage in short sales of the securities in the course of hedging the positions they assume with that selling stockholder, including, without limitation, in connection with distributions of the securities by those broker-dealers. The selling stockholders may enter into options or other transactions with broker-dealers that involve the delivery of the securities offered hereby to the broker-dealers, who may then resell or otherwise transfer those securities. The selling stockholders may also loan or pledge the securities offered hereby to a broker-dealer and the broker-dealer may sell the securities offered hereby so loaned or upon a default may sell or otherwise transfer the pledged securities offered hereby.

The selling stockholders and other persons participating in the sale or distribution of the securities will be subject to applicable provisions of the Exchange Act, and the rules and regulations thereunder, including Regulation M. This regulation may limit the timing of purchases and sales of any of the securities by the selling stockholders and any other person. The anti-manipulation rules under the Exchange Act may apply to sales of securities in the market and to the activities of the selling

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stockholders and their affiliates. Furthermore, Regulation M may restrict the ability of any person engaged in the distribution of the securities to engage in market-making activities with respect to the particular securities being distributed for a period of up to five business days before the distribution. These restrictions may affect the marketability of the securities and the ability of any person or entity to engage in market-making activities with respect to the securities.

Under the Registration Rights Agreement, we have agreed to indemnify the selling stockholders against certain liabilities that they may incur in connection with the sale of the securities registered hereunder, including liabilities under the Securities Act, and to contribute to payments that the selling stockholders may be required to make with respect thereto. In addition, we and the selling stockholders may agree to indemnify any underwriter, broker-dealer or agent against certain liabilities related to the selling of the securities, including liabilities arising under the Securities Act.

The securities offered hereby were originally issued to the selling stockholder pursuant to an exemption from the registration requirements of the Securities Act. We have agreed to maintain the effectiveness of this registration statement until the earlier of the fifth anniversary of the closing of the Archstone Portfolio Acquisition or when the aggregate market value of the securities held by the LBHI Group Members (as defined in the Registration Rights Agreement) is less than $250 million. We have agreed to pay all expenses in connection with this offering, but not including underwriting discounts, concessions, commissions or fees of the selling stockholders or any fees and expenses of counsel or other advisors to the selling stockholders. This summary of the terms of the Registration Rights Agreement and other statements relating thereto do not purport to be complete and is subject to, and qualified in its entirety by reference to, the full text of the Registration Rights Agreement, a copy of which has been filed as Exhibit 10.1 to this registration statement.

We will not receive any proceeds from sales of any securities by the selling stockholders.

We cannot assure you that the selling stockholders will sell all or any portion of the securities offered hereby.

To the extent permitted by applicable law, this plan of distribution may be modified in a prospectus supplement or otherwise. All of the foregoing may affect the marketability of the securities offered hereby. This offering will terminate on the date that all securities offered by this prospectus have been sold by the selling stockholders.

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Description of Common Stock

The following is a description of the material terms and provisions of our common stock. You should read our charter and bylaws in their entirety before you purchase any shares of our common stock.

General

Under our charter, we have authority to issue 140,000,000 shares of common stock, par value $.01 per share. Under Maryland law, stockholders generally are not responsible for our debts or obligations. As of February 28, 2013, we had 129,371,504 shares of common stock issued and outstanding. Our common stock is listed on the NYSE under the symbol "AVB."

Dividends

Subject to the preferential rights of any other class or series of stock and to the provisions of our charter regarding excess stock, which are described below, holders of shares of our common stock will be entitled to receive dividends on shares of common stock out of assets that we may legally use to pay dividends, if and when they are authorized and declared by our board of directors.

Voting rights

Except as otherwise required by law and except as provided by the terms of any other class or series of stock, holders of common stock have the exclusive power to vote on all matters presented to our stockholders, including the election of directors. Holders of common stock are entitled to one vote per share. There is no cumulative voting in the election of our directors, and, subject to any rights to elect directors that are granted to the holders of any class or series of preferred stock, the affirmative vote of the holders of a majority of all outstanding shares of common stock is required to elect a director.

Liquidation/dissolution rights

Subject to the preferential rights of any other class or series of stock and to the provisions of our charter regarding excess stock, holders of shares of our common stock share in the same proportion as our other stockholders in the assets that we may legally use to pay distributions in the event we are liquidated, dissolved or our affairs are wound up after we pay or make adequate provision for all of our known debts and liabilities.

Other rights

Subject to the preferential rights of any other class or series of stock and to provisions of our charter regarding excess stock, all shares of our common stock have equal dividend, distribution, liquidation and other rights, and have no preference, appraisal or exchange rights. Furthermore, holders of shares of our common stock have no conversion, sinking fund or redemption rights, or preemptive rights to subscribe for any of our securities.

Under Maryland law, a corporation generally cannot dissolve, amend its charter, merge, sell all or substantially all of its assets, engage in a share exchange or engage in similar transactions outside the ordinary course of business unless approved by the affirmative vote of stockholders holding at least two-thirds of the shares entitled to vote on the matter, unless a different percentage is set forth in the corporation's charter, which percentage shall not in any event be less than a majority of all of the shares entitled to vote on such matter. Our charter provides that whenever any vote of the holders of voting stock is required to amend or repeal any provision of the charter, then in addition to any other vote of the holders of voting stock that is required by the charter, (1) the affirmative vote of the

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holders of a majority of our outstanding shares of stock entitled to vote on such amendment or repeal, voting together as a single class, and (2) the affirmative vote of the holders of a majority of the outstanding shares of each class entitled to vote thereon as a class are required. However, with respect to the amendment or repeal of any of the provisions of our charter relating to the resignation or removal of directors, vacancies on the board of directors, independent directors, the rights and powers of our company, the board of directors and officers, and the limitation of liability of directors and officers, the affirmative vote of the holders of at least two-thirds of the outstanding shares entitled to vote on such amendment or repeal, voting together as a single class, and the affirmative vote of the holders of not less than two-thirds of the outstanding shares of each class entitled to vote thereon as a class, shall be required.

Restrictions on ownership

For us to qualify as a REIT under the Internal Revenue Code, no more than 50% in value of our outstanding capital stock may be owned, directly or indirectly, by or for five or fewer individuals at any time during the last half of a taxable year. To assist us in meeting this requirement, we may take actions such as the automatic conversion of shares in excess of this ownership restriction into shares of excess stock to limit the beneficial ownership of our outstanding equity securities, directly or indirectly, by one individual. See "Limits on Ownership of Stock."

Transfer Agent

The transfer agent and registrar for the common stock is Computershare Shareowner Services LLC, Canton, Massachusetts.

Limits on Ownership of Stock

Ownership limits

For us to qualify as a REIT under the Internal Revenue Code, among other things, no more than 50% in value of our outstanding capital stock may be owned, directly or indirectly, by or for five or fewer individuals at any time during the last half of a taxable year. Additionally, the shares of our capital stock must be beneficially owned by 100 or more persons during at least 335 days of a taxable year of twelve months or during a proportionate part of a shorter taxable year. To protect us against the risk of losing our status as a REIT due to a concentration of ownership among our stockholders, and to otherwise address concerns related to concentrated ownership of capital stock, our charter provides that no person may own (directly, indirectly by virtue of the attribution provisions of the Internal Revenue Code, or beneficially under Rule 13d-3 of the Securities Exchange Act) more than 9.8% of any class or series of our stock (15% for some entities as described below). Notwithstanding the preceding sentence, the board of directors at its option and in its sole discretion may approve ownership greater than the applicable ownership limitation by selected persons or entities. In connection with the Archstone Portfolio Acquisition, our board of directors provided an exemption to the ownership limitation for Jupiter, LBHI and any of their designated subsidiaries or affiliates. Our board of directors does not expect that it would waive the applicable ownership limit unless the board of directors receives evidence to its satisfaction that the waiver of the limit will not jeopardize our status as a REIT, and the board of directors also decides that the waiver is in our stockholders' best interests. Any transfer of shares of stock, including any security convertible into shares of stock, shall be void and have no effect if it: (1) would create a direct or indirect ownership of shares of stock in excess of the applicable ownership limit, absent a valid waiver of this ownership limit or (2) would result in our disqualification as a REIT, including any transfer that would (a) result in the shares of stock being owned by fewer than 100 persons, (b) result in us being "closely held" within the meaning of Section 856(h) of the Internal Revenue Code or (c) result in us constructively owning 10% or more of the ownership interests in a tenant within the meaning of Section 856(d)(2)(B) of the Internal

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Revenue Code. In addition, if any purported transfer of stock or any other event would otherwise result in any person violating the applicable ownership limit, then the purported transfer will be void and of no force or effect with respect to the intended transferee as to that number of shares in excess of the ownership limit. The intended transferee will acquire no right or interest in the excess shares; or, in the case of any event other than a purported transfer, the person holding record title to any shares in excess of the ownership limit shall cease to own any right or interest in the excess shares. In both cases, neither the intended transferee nor the person holding record title to any shares in excess of the ownership limit shall have any right to: (1) transfer or otherwise dispose of the excess stock, (2) vote the excess stock or (3) receive any dividend or distribution paid with respect to the excess stock, as further explained below.

Under the Internal Revenue Code, some types of entities, which includes pension plans described in Section 401(a) of the Internal Revenue Code and mutual funds registered under the Investment Company Act of 1940, will be looked through for purposes of the five or fewer test described above. Our charter limits these pension plans and mutual funds to owning no more than 15% of any class or series of our stock.

Shares owned in excess of the ownership limit

Stock owned, or deemed to be owned, or proposed to be transferred to a stockholder in excess of the ownership limit will be converted automatically into shares of excess stock and will be transferred, by operation of law, to a trust, the beneficiary of which shall be a qualified charitable organization selected by us. As soon as practicable after the transfer of shares to the trust, the trustee of the trust will be required to sell the shares of excess stock to a person who could own the shares without violating the ownership limit and distribute to the proposed transferee an amount equal to the lesser of (1) the price paid by the proposed transferee for the shares of excess stock or (2) the sales proceeds received by the trust for the shares of excess stock. In the case of any excess stock resulting from any event other than a transfer, or from a transfer for no consideration (such as a gift), the trustee will be required to sell the excess stock to a qualified person or entity and distribute to the person holding record title to the shares in excess of the ownership limit an amount equal to the lesser of (A) the fair market value of the excess stock as of the date of the event or (B) the sales proceeds received by the trust for the excess stock. In either case, any proceeds in excess of the amount distributable to the proposed transferee or person holding record title to the shares in excess of the ownership limit, as applicable, will be distributed to the beneficiary of the trust.

Upon the transfer of shares of excess stock by the trustee, the shares shall be converted automatically into an equal number of shares of the same class and series that were converted into the excess stock, and the shares of excess stock will be automatically retired and canceled and will thereupon be restored to the status of authorized but unissued shares of excess stock. Prior to a sale of any excess stock by the trustee, the trustee will be entitled to receive in trust for the beneficiary, all dividends and other distributions paid with respect to the excess stock. In addition, while the shares of excess stock are held in trust, the holder of shares will not be entitled to vote such shares, except when Maryland law mandates class voting rights. In the event voting rights are mandated by Maryland law, the trustee shall be entitled to vote the shares of excess stock.

Neither the proposed transferee nor any person holding record title to any excess stock shall have any right to receive any dividend or distribution paid with respect to the excess stock. Any dividend or distribution paid on excess stock prior to discovery by us of the violation of the applicable ownership limit shall be repaid to us. In addition, neither the proposed transferee nor any person holding record title to any excess stock shall have any voting rights with respect to the excess stock. Any vote of any excess stock prior to discovery by us of the violation of the applicable ownership limit shall, subject to applicable law, be rescinded and deemed void and shall be recast by the trustee acting for the benefit of the beneficiary; provided, however, that such vote shall not be rescinded and recast if we have

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already taken irreversible corporate action. Shares of excess stock are not treasury stock, but rather constitute a separate class of issued and outstanding stock.

Right to purchase excess stock

In addition to the foregoing transfer restrictions, we have the right for a period of 90 days to purchase all or any portion of the excess stock from the proposed transferee or any person holding record title to any excess stock for a price per share equal to the lesser of:

(1): the price per share initially paid for the stock by the proposed transferee or, in the case of excess stock resulting from any event other than a transfer or from a transfer for no consideration (such as a gift), the average of the closing price per share for the class of shares from which the shares of excess stock were converted for the five consecutive trading days ending on the date of such event or transfer, as applicable; or
(2): the average closing price per share for the class or series of shares from which the shares of excess stock were converted for the five consecutive trading days ending on the date we elect to purchase the shares.

The 90-day period begins on the date of the purported transfer or non-transfer event that violated the applicable ownership limit if the proposed transferee or person holding record title to any excess stock gives notice to us of the transfer or non-transfer event, as applicable, or if no notice is given, the date our board of directors determines that such a transfer has been made or such a non-transfer event has occurred.

General

The foregoing restrictions on transferability and ownership will not apply if our board of directors determines that it is no longer in our best interest to continue to qualify as a REIT. The board may, in its sole discretion, waive the ownership limits if evidence is presented that such ownership of shares in excess of the ownership limit will not jeopardize our qualification as a REIT and the board otherwise decides in its sole discretion that such action is in our stockholders' best interest.

Our stockholders are required to disclose to us in writing any information with respect to their ownership of our stock that we may request in order to determine our status as a REIT and to ensure compliance with the ownership limits.

The ownership limits may have the effect of delaying, deferring or preventing a change of control of our company.

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Federal Income Tax Considerations and Consequences of Your Investment

The following is a summary of certain material U.S. federal income tax considerations relating to our qualification as a REIT and the ownership and disposition of shares of our common stock.

Because this is a summary that is intended to address only certain material U.S. federal income tax considerations relating to the ownership and disposition of our common stock that will apply to all stockholders, it may not contain all the information that may be important to you. As you review this discussion, you should keep in mind that:

•: the tax consequences to you may vary depending on your particular tax situation;
•: special rules that are not discussed below may apply to you if, for example, you are a tax-exempt organization, a broker-dealer, a non-U.S. person, a trust, an estate, a regulated investment company, a financial institution, an insurance company, a pass-through entity or investor in such entities, a person holding shares of our common stock as part of a short sale, hedge, conversion, straddle, constructive sale or other integrated transaction for U.S. federal income tax purposes, a person subject to the alternative minimum tax, a U.S. stockholder whose "functional currency" (as defined in Section 985 of the Code) is not the U.S. dollar, or otherwise subject to special tax treatment under the Code;
•: this summary does not address state, local or non-U.S. tax considerations;
•: this summary deals only with common stockholders that hold common stock as a "capital asset" within the meaning of Section 1221 of the Code; and
•: this discussion is not intended to be, and should not be construed as, tax advice.

You are urged both to review the following discussion and to consult with your own tax advisor to determine the effect of ownership and disposition of our common stock on your individual tax situation, including any state, local or non-U.S. tax consequences.

The information in this section is based on the current Code, applicable Treasury regulations, the legislative history of the Code, current administrative interpretations and practices of the Internal Revenue Service (the "IRS"), including its practices and policies as endorsed in private letter rulings, which are not binding on the IRS except in the case of the taxpayer to whom a private letter ruling is addressed, and existing court decisions. Those authorities may be changed, possibly retroactively, or may be subject to differing interpretations, so as to result in U.S. federal income tax consequences different from those summarized below. Thus, it is possible that the IRS could challenge the statements in this discussion, which do not bind the IRS or the courts, and that a court could agree with the IRS. The following discussion describes the tax rules applicable to REITs as in effect as of the date of this prospectus and, with limited exceptions, does not address any rules that may have applied to us during prior periods.

Taxation of AvalonBay as a REIT

We have elected to be taxed as a REIT under the Code. A REIT generally is not subject to U.S. federal income tax on the income that it distributes to stockholders if it meets the applicable REIT distribution requirements and other requirements for qualification.

We believe that we are organized and have operated, and we intend to continue to operate, in a manner allowing us to qualify as a REIT, but there can be no assurance that we have qualified or will remain qualified as a REIT. Qualification and taxation as a REIT depend upon our ability to meet, through actual annual (or in some cases quarterly) operating results, requirements relating to income, asset ownership, distribution levels and diversity of share ownership, and the various other REIT qualification requirements imposed under the Code, as in effect for each applicable taxable period. Given the complex nature of the REIT qualification requirements, the ongoing importance of factual determinations and the possibility of future changes in our circumstances, we cannot provide any

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assurance that our actual operating results have satisfied or will satisfy the requirements for taxation as a REIT under the Code for any particular taxable year.

So long as we qualify for taxation as a REIT, we generally will not be subject to U.S. federal corporate income tax on our net income that is distributed currently to our stockholders. This treatment substantially eliminates "double taxation" (that is, taxation at both the corporate and stockholder levels) that generally results from an investment in a corporation. However, even if we qualify for taxation as a REIT, we will be subject to U.S. federal income tax as follows:

•

we will be taxed at regular corporate rates on any undistributed "REIT taxable income." REIT taxable income is the taxable income of the REIT, subject to specified adjustments, including a deduction for dividends paid;

•

under some circumstances, we may be subject to the "alternative minimum tax" on our items of tax preference;

•

if we have net income from the sale or other disposition of "foreclosure property" that is held primarily for sale to customers in the ordinary course of business, or other nonqualifying income from foreclosure property, we will be subject to tax at the highest corporate rate on this income;

•

our net income from "prohibited transactions" will be subject to a 100% tax. In general, prohibited transactions are sales or other dispositions of property (other than foreclosure property) held primarily for sale to customers in the ordinary course of business unless such property has been held by us for two years or more and certain other requirements are satisfied;

•

if we fail to satisfy either the 75% gross income test or the 95% gross income test discussed below, but nonetheless maintain our qualification as a REIT because other requirements are met, we will be subject to a tax equal to the greater of (1) the amount by which 75% of our gross income exceeds the amount of our income qualifying under the 75% test for the taxable year or (2) the amount by which 95% of our gross income exceeds the amount of our income qualifying for the 95% income test for the taxable year, multiplied by a fraction intended to reflect our profitability;

•

if we fail to satisfy any of the asset tests (other than a failure by a de minimis amount of the 5% or 10% asset tests) and we qualify for and satisfy certain cure provisions, then we will have to pay an excise tax equal to the greater of (1) $50,000 and (2) an amount determined by multiplying (x) the net income generated during a specified period by the assets that caused the failure by (y) the highest U.S. federal income tax rate applicable to corporations;

•

if we fail to satisfy any REIT requirements other than the income test or asset test requirements and we qualify for a reasonable cause exception, then we may retain our REIT qualification, but we will have to pay a penalty equal to $50,000 for each such failure;

•

we will be subject to a nondeductible 4% excise tax on the excess of the required distributions over the sum of amounts actually distributed and amounts retained for which U.S. federal income tax was paid, if we fail to distribute during each calendar year at least the sum of:

(1): 85% of our REIT ordinary income for the year;
(2): 95% of our REIT capital gain net income for the year; and
(3): any undistributed taxable income from prior taxable years;

•

we will be subject to a 100% penalty tax on some payments we receive (or on certain expenses deducted by a taxable REIT subsidiary) if arrangements among us, our tenants and our taxable REIT subsidiaries are not comparable to similar arrangements among unrelated parties;

•

if we should acquire any asset from a "C" corporation in a carry-over basis transaction and we subsequently recognize gain on the disposition of such asset during the ten-year recognition period beginning on the date on which we acquired the asset, then, to the extent of any built-in

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gain, such gain will be subject to tax at the highest regular corporate rate. Built-in gain is the excess of (x) the fair market value of the asset as of the beginning of the applicable recognition period over (y) the adjusted basis in such asset as of the beginning of such recognition period;

•: income earned by our taxable REIT subsidiaries will be subject to tax at regular corporate rates; and
•: we may be required to pay penalties to the IRS in certain circumstances, including if we fail to meet recordkeeping requirements intended to monitor our compliance with rules relating to the composition of our shareholders.

�� Requirements for qualification as a REIT. We elected to be taxable as a REIT for U.S. federal income tax purposes for our taxable year ended December 31, 1994 and for all subsequent taxable years. In order to have so qualified, we must have met and continue to meet the requirements discussed below, relating to our organization, ownership, sources of income, nature of assets and distributions of income to stockholders.

The Code defines a REIT as a corporation, trust or association:

(1): that is managed by one or more trustees or directors;
(2): the beneficial ownership of which is evidenced by transferable shares, or by transferable certificates of beneficial interest;
(3): that would be taxable as a domestic corporation, but for Sections 856 through 859 of the Code;
(4): that is neither a financial institution nor an insurance company subject to applicable provisions of the Code;
(5): the beneficial ownership of which is held by 100 or more persons;
(6): not more than 50% in value of the outstanding shares of which is owned during the last half of each taxable year, directly or indirectly, by five or fewer individuals, as defined in the Code to include specified entities;
(7): that makes an election to be taxable as a REIT, or has made this election for a previous taxable year which has not been revoked or terminated, and satisfies all relevant filing and other administrative requirements established by the IRS that must be met to elect and maintain REIT status;
(8): that uses a calendar year for U.S. federal income tax purposes and complies with the recordkeeping requirements of the Code and regulations promulgated thereunder; and
(9): that meets other applicable tests, described below, regarding the nature of its income and assets and the amount of its distributions.

Conditions (1), (2), (3) and (4) above must be met during the entire taxable year and condition (5) above must be met during at least 335 days of a taxable year of 12 months, or during a proportionate part of a taxable year of less than 12 months. For purposes of determining stock ownership under condition (6) above, a supplemental unemployment compensation benefits plan, a private foundation and a portion of a trust permanently set aside or used exclusively for charitable purposes generally are each considered an individual. A trust that is a qualified trust under Code Section 401(a) generally is not considered an individual, and beneficiaries of a qualified trust are treated as holding shares of a REIT in proportion to their actuarial interests in the trust for purposes of condition (6) above.

We believe that we have issued sufficient shares of common stock with sufficient diversity of ownership to allow us to satisfy conditions (5) and (6) above. In addition, our charter contains restrictions regarding the transfer of shares of common stock and preferred stock that are intended to assist us in continuing to satisfy the share ownership requirements described in conditions (5) and

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(6) above. These restrictions, however, may not ensure that we will be able to satisfy these share ownership requirements.

To monitor its compliance with condition (6) above, a REIT is required to send annual letters to its stockholders requesting information regarding the actual ownership of its shares. If we comply with the annual letters requirement and we do not know or, exercising reasonable diligence, would not have known of our failure to meet condition (6) above, then we will be treated as having met condition (6) above.

Qualified REIT Subsidiaries. If a REIT owns a corporate subsidiary that is a "qualified REIT subsidiary," the separate existence of that subsidiary will be disregarded for U.S. federal income tax purposes. Generally, a qualified REIT subsidiary is a corporation, other than a taxable REIT subsidiary (discussed below), all of the stock of which is owned by the REIT. All assets, liabilities and items of income, deduction and credit of the qualified REIT subsidiary will be treated as assets, liabilities and items of income, deduction and credit of the REIT itself. A qualified REIT subsidiary of AvalonBay will not be subject to federal corporate income taxation, although it may be subject to state and local taxation in some states.

Taxable REIT Subsidiaries. A "taxable REIT subsidiary" of AvalonBay is a corporation in which we directly or indirectly own stock and that elects, together with us, to be treated as a taxable REIT subsidiary under Section 856(l) of the Code. In addition, if one of our taxable REIT subsidiaries owns, directly or indirectly, securities representing more than 35% or more of the vote or value of a subsidiary corporation, that subsidiary will also be treated as our taxable REIT subsidiary. A taxable REIT subsidiary is a corporation subject to U.S. federal income tax, and state and local income tax where applicable, as a regular "C" corporation.

Generally, a taxable REIT subsidiary can perform some impermissible tenant services without causing us to receive impermissible tenant services income under the REIT income tests. A taxable REIT subsidiary also can recognize income that would be subject to the 100% prohibited transaction tax, or income that would be nonqualifying income under the gross income tests, if earned by a REIT. However, several provisions regarding the arrangements between a REIT and its taxable REIT subsidiaries ensure that a taxable REIT subsidiary will be subject to an appropriate level of U.S. federal income tax. For example, a taxable REIT subsidiary is limited in its ability to deduct interest payments made to us in excess of a certain amount. In addition, we will be obligated to pay a 100% penalty tax on some payments that we receive or on certain expenses deducted by the taxable REIT subsidiary if the economic arrangements among us, our tenants and the taxable REIT subsidiary are not comparable to similar arrangements among unrelated parties.

Ownership of Partnership Interests by a REIT. A REIT that is a partner in a partnership (or a member in a limited liability company or other entity that is treated as a partnership for U.S. federal income tax purposes) will be deemed to own its proportionate share of the assets of the partnership and will be deemed to earn its proportionate share of the partnership's income. The assets and gross income of the partnership retain the same character in the hands of the REIT for purposes of the gross income and asset tests applicable to REITs as described below. Thus, our proportionate share of the assets and items of income of any entity taxable as a partnership for U.S. federal income tax purposes in which we hold an interest will be treated as our assets and liabilities and our items of income for purposes of applying the requirements described in this prospectus. The assets, liabilities and items of income of any partnership in which we own an interest include such entity's share of the assets and liabilities and items of income with respect to any partnership in which it holds an interest. In that regard, the assets of one of our joint ventures with Equity Residential include indirect interests in partnerships controlled by Equity Residential, and thus for purposes of our compliance with the REIT asset and gross income requirements we will be treated as owning our proportionate share of the assets of the Equity Residential partnerships in which the joint venture has an interest. Although Equity Residential has agreed to operate those partnerships in compliance with the REIT

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requirements, we cannot assure you that such Equity Residential partnerships will be operated in compliance with the REIT requirements. Failure by those partnerships to comply with the REIT requirements could potentially jeopardize our REIT status.

The discussion above does not apply to our interest in any partnership or other unincorporated entity treated as a corporation for U.S. federal income tax purposes. If an entity that we treated as a partnership for U.S. federal income tax purposes and the REIT requirements were determined instead to be taxed as a corporation, we could fail one or more of the REIT income and asset tests described below. Generally, a domestic unincorporated entity with two or more owners is treated as a partnership for U.S. federal income tax purposes unless it affirmatively elects to be treated as a corporation. However, certain "publicly traded partnerships" are treated as corporations for U.S. federal income tax purposes. A "publicly traded partnership" is any partnership (i) the interests in which are traded on an established securities market or (ii) the interests in which are readily tradable on a "secondary market or the substantial equivalent thereof." However, under the relevant Treasury Regulations, interests in a partnership will not be considered readily tradable on a secondary market or on the substantial equivalent of a secondary market if the partnership qualifies for specified "safe harbors," which are based on the specific facts and circumstances relating to the partnership. Moreover, certain publicly traded partnerships will avoid being treated as a corporation for U.S. federal income tax purposes if the partnership derives at least 90% of its gross income from certain specified sources of "qualifying income." We do not believe that any of our direct or indirect subsidiary partnerships should be treated as corporations under the publicly traded partnership rules. However, a contrary determination could prevent us from qualifying as a REIT.

Income Tests Applicable to REITs. To qualify as a REIT, we must satisfy two gross income tests annually. First, at least 75% of our gross income, excluding gross income from prohibited transactions and certain other income and gains described below, for each taxable year must be derived directly or indirectly from investments relating to real property or mortgages on real property, including "rents from real property," gains on the disposition of real estate assets, dividends paid by another REIT and interest on obligations secured by mortgages on real property or on interests in real property, income and gain derived from foreclosure property, or from some types of temporary investments. Second, at least 95% of our gross income, excluding gross income from prohibited transactions and certain other income and gains described below, for each taxable year must be derived from any combination of income qualifying under the 75% test and dividends, interest, and gain from the sale or disposition of stock or securities. See "—Hedging Transactions and Foreign Currency Gains".

Rents received by us will qualify as rents from real property for purposes of the REIT gross income tests described above only if several conditions are met. First, the amount of rent must not be based in whole or in part on the income or profits of any person. However, an amount received or accrued generally will not be excluded from the term "rents from real property" solely by reason of being based on a fixed percentage or percentages of receipts or sales. Second, rents received from a "related party tenant" (as defined below) will not qualify as rents from real property for purposes of the REIT gross income tests unless the tenant is a taxable REIT subsidiary and (1) at least 90% of the property is leased to unrelated tenants and the rent paid by the taxable REIT subsidiary is substantially comparable to the rent paid by the unrelated tenants for comparable space, or (2) the property leased to the taxable REIT subsidiary is a hotel or a health care facility and certain other requirements are satisfied. A tenant is a related party tenant if the REIT, or an actual or constructive owner of 10% or more of the REIT, actually or constructively owns 10% or more of the tenant. Third, if rent attributable to personal property, leased in connection with a lease of real property, is greater than 15% of the total rent received under the lease, then the portion of rent attributable to the personal property will not qualify as rents from real property.

Generally, for rents to qualify as rents from real property for purposes of the REIT gross income tests, we may provide directly only an insignificant amount of services, unless those services are

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"customarily furnished or rendered" in connection with the rental of real property and not otherwise considered "rendered to the occupant." Accordingly, we may not provide "impermissible tenant services" to tenants (except through an independent contractor from whom we derive no income and that meets other requirements or through a taxable REIT subsidiary) without giving rise to "impermissible tenant service income." Impermissible tenant service income is deemed to be at least 150% of our direct cost of providing the service. If the impermissible tenant service income exceeds 1% of our total income from a property, then all of the income from that property will fail to qualify as rents from real property. If the total amount of impermissible tenant service income from a property does not exceed 1% of our total income from the property, the services will not "taint" the other income from the property (that is, it will not cause the rent paid by tenants of that property to fail to qualify as rents from real property), but the impermissible tenant service income will not qualify as rents from real property.

We believe that the amount of annual rent that is not treated as rents from real property under the above rules will not jeopardize our status as a REIT. We have provided and expect to continue to provide services at our multifamily apartment communities. We believe that the services with respect to our communities that have been and will be provided by us directly are usually or customarily rendered in connection with the rental of space for occupancy only and are not otherwise rendered to particular tenants, or, if considered impermissible tenant services, income from the provision of such services with respect to a given property has not and will not jeopardize our status as a REIT. We believe that any services with respect to our communities that may not be provided by us directly without jeopardizing our status as a REIT have been, and, if applicable, will continue to be, performed by independent contractors or taxable REIT subsidiaries.

As a result of the Archstone Portfolio Acquisition we have increased the amount of assets and activities in our taxable REIT subsidiaries, and we may in the future acquire equity interests in additional taxable REIT subsidiaries. Taxable dividends from a taxable REIT subsidiary and gain from a sale or other taxable disposition of interests in a taxable REIT subsidiary will qualify under the 95% income test, but not the 75% income test. Our need to satisfy the 75% income test may adversely affect our ability to distribute earnings from, or dispose of our investment in, a taxable REIT subsidiary.

We have earned and continue to earn amounts of nonqualifying income. For example, we earn fees related to the development and management of properties that are not wholly-owned by us. We believe that the amount of nonqualifying income generated from these and certain other activities has not affected and will not affect our ability to meet the gross income tests.

Any gain we realize on the sale of any property held as inventory or other property held primarily for sale to customers in the ordinary course of business will be treated as income from a prohibited transaction that is subject to a 100% penalty tax, unless such property has been held by us for two years and certain other requirements are satisfied or the gain is realized in a taxable REIT subsidiary. Under existing law, whether property is held as inventory or primarily for sale to customers in the ordinary course of a trade or business is a question of fact that depends on all the facts and circumstances of a particular transaction. We generally intend to hold our properties for investment with a view to long-term appreciation, to engage in the business of acquiring, developing, owning and operating properties, and to make occasional sales of properties, consistent with our investment objectives. We cannot provide any assurance, however, that the IRS might not contend that one or more of these sales are subject to the 100% penalty tax. We intend to hold assets developed or held for sale in taxable REIT subsidiaries. Although a taxable REIT subsidiary is not subject to the 100% penalty tax, it does pay tax on its taxable income and gains at regular corporate rates.

If we fail to satisfy one or both of the 75% or 95% gross income tests for any taxable year, we may nevertheless qualify as a REIT for that year if we are entitled to relief under the Code. These relief provisions generally will be available if our failure to meet the tests is due to reasonable cause

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and not due to willful neglect and, following our identification of such failure for any taxable year, we file a schedule describing each item of our gross income for such taxable year described in the gross income tests in accordance with the applicable Treasury Regulations. It is not possible, however, to state whether in all circumstances we would be entitled to the benefit of these relief provisions. For example, if we fail to satisfy the gross income tests because nonqualifying income that we intentionally incur exceeds the limits on nonqualifying income, the IRS could conclude that the failure to satisfy the tests was not due to reasonable cause. If we are not entitled to relief under these provisions, we will fail to qualify as a REIT. As discussed under "—Taxation of AvalonBay as a REIT" even if these relief provisions apply, we would be subject to tax to the extent we fail to meet the REIT gross income tests.

Asset Tests Applicable to REITs. At the close of each quarter of our taxable year, we must satisfy four tests relating to the nature of our assets:

(1): at least 75% of the value of our total assets must be represented by real estate assets, cash, cash items and government securities. Real estate assets include, for this purpose, stock or debt instruments held for less than one year that are purchased with the proceeds from an offering of our shares or a public offering of our debt with a term of five years or more and shares in other qualifying REITs;
(2): not more than 25% of our total assets may be represented by securities other than those in the 75% asset class;
(3): except for investments in qualified REIT subsidiaries, taxable REIT subsidiaries, equity interests in REITs or other securities that qualify as "real estate assets" for purposes of the test described in clause (1): the value of any one issuer's securities owned by us may not exceed 5% of the value of our total assets; we may not own securities possessing more than 10% of the voting power of any one issuer's outstanding securities; and we may not own more than 10% of the value of the outstanding securities of any one issuer; and
(4): not more than 25% of the value of our total assets may be represented by securities of one or more taxable REIT subsidiaries.

Securities for purposes of the asset tests may include debt securities. However, the 10% value test does not apply to certain "straight debt" and other excluded securities, as described in the Code including, but not limited to, any loan to an individual or estate, any obligation to pay rents from real property and any security issued by a REIT. In addition, (1) a REIT's interest as a partner in a partnership is not considered a security for purposes of applying the 10% value test to securities issued by the partnership; (2) any debt instrument issued by a partnership (other than straight debt or another excluded security) will not be considered a security issued by the partnership if at least 75% of the partnership's gross income is derived from sources that would qualify for the 75% gross income test; and (3) any debt instrument issued by a partnership (other than straight debt or another excluded security) will not be considered a security issued by the partnership to the extent of the REIT's interest as a partner in the partnership. In general, straight debt is defined as a written, unconditional promise to pay on demand or at a specific date a fixed principal amount, and the interest rate and payment dates on the debt must not be contingent on profits or the discretion of the debtor. In addition, straight debt may not contain a convertibility feature. Stock of our taxable REIT subsidiaries does not qualify as a real estate asset under the REIT rules.

We believe that we have complied and will be able to continue to comply with the applicable asset tests with respect to each such issuer. In this regard, however, we cannot provide any assurance that the IRS might not disagree with our determinations.

After initially meeting the asset tests at the close of any quarter, we will not lose our status as a REIT if we fail to satisfy any of the asset tests (other than the 10% voting limitation) at the end of a later quarter solely by reason of changes in the relative values of our assets. If the failure to satisfy any such asset tests results from an acquisition of securities or other property during a quarter, the failure

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can be cured by disposition of sufficient non-qualifying assets within 30 days after the close of that quarter. We intend to maintain adequate records of the value of our assets to ensure compliance with the asset tests and to take any available actions within 30 days after the close of any quarter as may be required to cure any noncompliance with the asset tests.

Moreover, if we fail to satisfy any of the asset tests at the end of a calendar quarter during a taxable year and such failure is not cured within 30 days as described above, we will not lose our REIT status if one of the following additional exceptions applies: (1) the failure is due to a violation of the 5% or 10% asset tests and is "de minimis" (for this purpose, a "de minimis" failure is one that arises from our ownership of assets the total value of which does not exceed the lesser of 1% of the total value of our assets at the end of the quarter in which the failure occurred and $10 million) and we either dispose of the assets that caused the failure or otherwise satisfy any of the asset tests within 6 months after the last day of the quarter in which our identification of the failure occurred; or (2) the failure is due to a violation of any of the asset tests (other than "de minimis" violations of the 5% or 10% asset tests) and all of the following requirements are satisfied: (i) the failure is due to reasonable cause and not willful neglect, (ii) we file a schedule in accordance with Treasury Regulations providing a description of each asset that caused the failure, and (iii) we either dispose of the assets that caused the failure or otherwise satisfy the asset tests within 6 months after the last day of the quarter in which our identification of the failure occurred. If we must rely on the reasonable cause exception for "de minimis" failures, we must pay an excise tax equal to the greater of (x) $50,000 and (y) an amount determined by multiplying the net income generated during a specified period by the assets that caused the failure by the highest U.S. federal income tax applicable to corporations.

Foreclosure Property. Foreclosure property is real property (including interests in real property) and any personal property incident to such real property (1) that is acquired by a REIT as a result of the REIT having bid in the property at foreclosure, or having otherwise reduced the property to ownership or possession by agreement or process of law, after there was a default (or default was imminent) on a lease of the property or a mortgage loan held by the REIT and secured by the property, (2) for which the related loan or lease was made, entered into or acquired by the REIT at a time when default was not imminent or anticipated and (3) for which such REIT makes an election to treat the property as foreclosure property. REITs generally are subject to tax at the maximum corporate rate (currently 35%) on any net income from foreclosure property, including any gain from the disposition of the foreclosure property, other than income that would otherwise be qualifying income for purposes of the 75% gross income test. Any gain from the sale of property for which a foreclosure property election has been made will not be subject to the 100% tax on gains from prohibited transactions described above, even if the property is held primarily for sale to customers in the ordinary course of a trade or business.

Hedging Transactions and Foreign Currency Gains. We may enter into hedging transactions with respect to one or more of our assets or liabilities. Hedging transactions could take a variety of forms, including interest rate swaps or cap agreements, options, futures contracts, forward rate agreements or similar financial instruments. Except to the extent as may be provided by future Treasury regulations, any income from a hedging transaction which is clearly identified as such before the close of the day on which it was acquired, originated or entered into, including gain from the disposition or termination of such a transaction, will not constitute gross income for purposes of the 95% and 75% income tests, provided that the hedging transaction is entered into after July 30, 2008 (1) in the normal course of our business primarily to manage risk of interest rate or price changes or currency fluctuations with respect to indebtedness incurred or to be incurred by us to acquire or carry real estate assets or (2) primarily to manage the risk of currency fluctuations with respect to any item of income or gain that would be qualifying income under the 75% or 95% income tests (or any property which generates such income or gain). To the extent we enter into other types of hedging transactions, the income from those transactions is likely to be treated as nonqualifying income for purposes of both the 75% and 95%

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gross income tests. We intend to structure any hedging transactions in a manner that does not jeopardize our ability to qualify as a REIT. In addition, certain foreign currency gains may be excluded from gross income for purposes of one or both of the REIT gross income tests, provided we do not deal in or engage in substantial and regular trading in securities.

Annual Distribution Requirements Applicable to REITs. To qualify as a REIT, we are required to distribute dividends, other than capital gain dividends, to our stockholders each year in an amount at least equal to (1) the sum of (a) 90% of our REIT taxable income, computed without regard to the dividends paid deduction and our net capital gain, and (b) 90% of the net income, after tax, from foreclosure property, minus (2) the sum of certain specified items of noncash income. For purposes of the distribution requirements, any built-in gain (net of the applicable tax) we recognize during the applicable recognition period that existed on an asset when we acquired it from a C corporation in a carry-over basis transaction will be included in our REIT taxable income under Treasury regulations. See "—Taxation of AvalonBay as a REIT" for a discussion of the possible recognition of built-in gain. These distributions must be paid either in the taxable year to which they relate, or in the following taxable year if declared before we timely file our tax return for the prior year and if paid with or before the first regular dividend payment date after the declaration is made.

To qualify as a REIT, we cannot have at the end of any taxable year any undistributed earnings and profits that are attributable to a non-REIT taxable year. To the extent we acquire any non-REIT earnings and profits, including through the Archstone Portfolio Acquisition, we intend to distribute any such earnings and profits before the end of the applicable taxable year. Distributions of non-REIT earnings and profits do not count towards the above 90% minimum distribution requirement or reduce our retained income and gain subject to corporate tax.

We believe that we have made and intend to continue to make timely distributions sufficient to satisfy the annual distribution requirements.

Generally, we anticipate having sufficient cash or liquid assets to enable us to satisfy the 90% distribution requirement. It is possible, however, that we, from time to time, may choose to retain cash to fund capital projects or future operations or may not have sufficient cash or other liquid assets to meet this distribution requirement or to distribute such greater amount as may be necessary to avoid income and excise taxation, in part due to timing differences between (a) the actual receipt of income and the actual payment of deductible expenses and (b) the inclusion of such income and the deduction of such expenses in arriving at our taxable income, or as a result of nondeductible expenses such as principal amortization or capital expenditures in excess of noncash deductions. In such event, we may find it necessary to arrange for borrowings or pay taxable stock dividends in order to meet the distribution requirement.

Under some circumstances, we may be able to rectify a failure to meet the distribution requirement for a year by paying dividends to stockholders in a later year, which may be included in our deduction for dividends paid for the earlier year. We will refer to such dividends as "deficiency dividends." Thus, we may be able to avoid being taxed on amounts distributed as deficiency dividends. We will, however, be required to pay interest based upon the amount of any deduction taken for deficiency dividends.

To the extent that we do not distribute all of our net capital gain or distribute at least 90%, but less than 100%, of our REIT taxable income, as adjusted, we will be subject to tax on these retained amounts at regular corporate tax rates.

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We will be subject to a nondeductible 4% excise tax on the excess of the required distributions over the sum of amounts actually distributed and amounts retained for which U.S. federal income tax was paid, if we fail to distribute during each calendar year at least the sum of:

(1): 85% of our REIT ordinary income for the year;
(2): 95% of our REIT capital gain net income for the year; and
(3): any undistributed taxable income from prior taxable years.

A REIT may elect to retain rather than distribute all or a portion of its net capital gains and pay tax on the gains. In that case, a REIT may elect to have its stockholders include their proportionate share of the undistributed net capital gains in income as long-term capital gains and receive a credit for their share of the tax paid by the REIT. For purposes of the 4% excise tax described above, any such retained amounts would be treated as having been distributed.

Record-Keeping Requirements. We are required to comply with applicable record-keeping requirements. Failure to comply could result in monetary fines.

Failure of AvalonBay to Qualify as a REIT. If we fail to satisfy any REIT requirements (other than the income test or asset test requirements, to which specific cure provisions apply), we generally will avoid disqualification as a REIT if the failure is due to reasonable cause and not due to willful neglect and we pay a penalty of $50,000 with respect to such failure. It is not possible to state whether in all circumstances we would be entitled to such statutory relief.

If we fail to qualify for taxation as a REIT in any taxable year and the relief provisions do not apply, we will be subject to tax on our taxable income at regular corporate rates, including any applicable alternative minimum tax. Distributions to stockholders in any year in which we fail to qualify will not be deductible by us nor will they be required to be made. In such event, to the extent of current or accumulated earnings and profits, all distributions to stockholders will be taxable as dividend income. Subject to limitations of the Code, corporate stockholders may be eligible for the dividends-received deduction and non-corporate stockholders may be eligible to treat the dividends received from us as qualified dividend income taxable as net capital gains under the provisions of Section 1(h)(11) of the Code. Unless we are entitled to relief under specific statutory provisions, we also will be disqualified from electing to be taxed as a REIT for the four taxable years following the year during which qualification was lost.

Taxation of U.S. Stockholders

When we refer to a U.S. stockholder, we mean a beneficial owner of our common stock that is, for United States federal income tax purposes:

(1): a citizen or resident, as defined in Code Section 7701(b), of the United States;
(2): a corporation, or other entity treated as a corporation for federal income tax purposes, created or organized under the laws of the United States, any state or the District of Columbia;
(3): an estate the income of which is subject to federal income taxation regardless of its source; or
(4): a trust that is subject to the primary supervision of a United States court and the control of one or more U.S. persons or that has a valid election in effect under the applicable Treasury Regulations to be treated as a U.S. person under the Code.

Generally, in the case of a partnership (or other entity treated as such for federal income tax purposes) that holds our common stock, any partner that would be a U.S. stockholder if it held the

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common stock directly is also a U.S. stockholder. A "non-U.S. stockholder" is a holder that is a nonresident alien individual or a foreign corporation for U.S. federal income tax purposes.

Distributions by AvalonBay. So long as we qualify as a REIT, distributions to U.S. stockholders out of our current or accumulated earnings and profits that are not designated as capital gain dividends will be taxable as dividend income. In general, our dividends will not be eligible for the dividends received deduction generally available for corporations and will not qualify for treatment as qualified dividend income taxed as net capital gain by non-corporate stockholders. Distributions in excess of our current and accumulated earnings and profits will not be taxable to a U.S. stockholder to the extent that the distributions do not exceed the adjusted tax basis of the stockholder's shares. Rather, such distributions will reduce the adjusted basis of such shares. Distributions in excess of current and accumulated earnings and profits that exceed a U.S. stockholder's adjusted basis in its shares will be treated as gain from the sale or exchange of such shares, taxable as capital gains in the amount of such excess if the shares are held as a capital asset. If we declare a dividend in October, November or December of any year with a record date in one of these months and pay the dividend on or before January 31 of the following year, we will be treated as having paid the dividend, and our stockholders will be treated as having received the dividend, on December 31 of the year in which the dividend was declared. The above applies regardless of whether the distributions by us are reinvested pursuant to the Dividend Reinvestment and Stock Purchase Plan. This discussion applies equally to distributions payable in cash and taxable stock distributions.

We may elect to designate distributions of our net capital gain as "capital gain dividends." Capital gain dividends generally are taxed to U.S. stockholders as gain from the sale or exchange of a capital asset held for more than one year, without regard to how long the U.S. stockholder has held its shares. Designations made by us will be effective only to the extent that they comply with the principles of Revenue Ruling 89-81, which require that distributions made to different classes of shares be composed proportionately of dividends of a particular type. If we designate any portion of a dividend as a capital gain dividend, a U.S. stockholder will receive an IRS Form 1099-DIV indicating the amount that will be taxable to the stockholder as capital gain. Corporate stockholders, however, may be required to treat up to 20% of capital gain dividends as ordinary income.

Instead of paying capital gain dividends, we may choose to retain all or part of our net capital gain and designate such amount as "undistributed capital gain." We will be subject to tax at regular corporate rates on any undistributed capital gains and our earnings and profits will be adjusted appropriately. On such a designation, a U.S. stockholder:

(1): will include in its income as long-term capital gains its proportionate share of such undistributed capital gains;
(2): will be deemed to have paid its proportionate share of the tax paid by us on such undistributed capital gains and receive a credit or a refund to the extent that the tax paid by us exceeds the U.S. stockholder's tax liability on the undistributed capital gains; and
(3): will increase the basis in its common stock by the difference between the amount of capital gain included in its income and the amount of tax it is deemed to have paid.

We will classify portions of any designated capital gain dividend or undistributed capital gains as either (1) a 20% rate gain distribution, which would be taxable to non-corporate U.S. stockholders at a maximum rate of 20% or (2) an "unrecaptured Section 1250 gain" distribution, which would be taxable to non-corporate U.S. stockholders at a maximum rate of 25%. We must determine the maximum amounts that we may designate as 20% and 25% rate capital gain dividends by performing the computation required by the Code as if the REIT were an individual whose ordinary income were subject to a marginal tax rate in excess of 25%.

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Distributions made by us and gain arising from the sale or exchange by a U.S. stockholder of shares of our common stock will not be treated as passive activity income, and as a result, U.S. stockholders generally will not be able to apply any "passive losses" against this income or gain. In addition, with respect to our non-corporate U.S. stockholders, dividends (other than capital gain dividends and dividends taxed at net capital gains rates) generally will be treated as investment income for purposes of the investment interest limitations. A U.S. stockholder may elect to treat capital gain dividends and capital gains from the disposition of shares of our common stock as investment income for purposes of the investment interest limitation, in which case such amounts otherwise taxable as capital gains will be taxed at ordinary income rates. We will notify stockholders regarding the portions of distributions for each year that constitute ordinary income, qualified dividend income (if any), return of capital and capital gain. U.S. stockholders may not include in their own income tax returns any of our net operating losses or capital losses.

Sales of Shares. Upon any taxable sale or other disposition of shares, a U.S. stockholder will recognize gain or loss for U.S. federal income tax purposes in an amount equal to the difference between (x) the amount of cash and the fair market value of any property received on the sale or other disposition and (y) the holder's adjusted basis in the shares for tax purposes. This gain or loss will be a capital gain or loss if the shares have been held by the U.S. stockholder as a capital asset. The applicable tax rate will depend on the stockholder's holding period in the shares (generally, if an asset has been held for more than one year it will produce long-term capital gain) and the stockholder's tax bracket. The IRS has the authority to prescribe, but has not yet prescribed, regulations that would apply a capital gain tax rate of 25% (which is generally higher than the long-term capital gain tax rates for non-corporate stockholders) to a portion of capital gain realized by a non-corporate stockholder on the sale of REIT shares that would correspond to the REIT's "unrecaptured Section 1250 gain." Stockholders are urged to consult with their own tax advisors with respect to their capital gain tax liability. A corporate U.S. stockholder will be subject to tax at a maximum rate of 35% on capital gain from the sale of our common stock. In general, any loss recognized by a U.S. stockholder upon the sale or other disposition of shares that have been held for six months or less, after applying the holding period rules, will be treated as a long-term capital loss, to the extent of distributions received by the U.S. stockholder from us that were required to be treated as long-term capital gains. All or a portion of any loss realized upon a taxable disposition of shares may be disallowed if other shares are purchased within 30 days before or after the date of disposition.

Medicare Tax on Unearned Income. A U.S. stockholder that is an individual is subject to a 3.8% tax on the lesser of (1) his or her "net investment income" for the relevant taxable year or (2) the excess of his or her modified gross income for the taxable year over a certain threshold (between $125,000 and $250,000 depending on the individual's U.S. federal income tax filing status). A similar regime applies to certain estates and trusts. Net investment income generally would include dividends on our common stock and gain from the sale of our common stock. If you are a U.S. investor that is an individual, an estate or a trust, you are urged to consult your tax advisors regarding the applicability of this tax to your income and gains in respect of your investment in our common stock.

Taxation of Tax-Exempt Stockholders

Provided that a tax-exempt stockholder has not held its common stock as "debt financed property" within the meaning of the Code, the dividend income from our company will not be unrelated business taxable income, referred to as UBTI, to a tax-exempt stockholder. Similarly, gain from the sale of shares will not constitute UBTI unless the tax-exempt stockholder has held its shares as debt financed property within the meaning of the Code or is a dealer in the shares.

However, for tax-exempt stockholders that are social clubs, voluntary employee benefit associations, supplemental unemployment benefit trusts or qualified group legal services plans exempt from U.S. federal income taxation under Sections 501(c)(7), (c)(9), (c)(17) or (c)(20) of the Code,

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respectively, income from an investment in our company will generally constitute UBTI; however, an organization exempt under Section 501(c)(9), (c)(17) or (c)(20) of the Code may reduce UBTI if it properly sets aside or reserves such amounts for purposes specified in the Code. These tax-exempt stockholders should consult their own tax advisors concerning these "set aside" and reserve requirements.

Notwithstanding the above, however, a portion of the dividends paid by a "pension-held REIT" are treated as UBTI if received by any trust which is described in Section 401(a) of the Code, is tax-exempt under Section 501(a) of the Code and holds more than 10%, by value, of the interests in the REIT.

Tax-exempt pension funds that are described in Section 401(a) of the Code are referred to below as "pension trusts."

A REIT is a pension-held REIT if it meets the following two tests:

(1): it qualified as a REIT only by reason of Section 856(h)(3) of the Code, which provides that stock owned by pension trusts will be treated, for purposes of determining if the REIT is closely held, as owned by the beneficiaries of the trust rather than by the trust itself; and
(2): either (a) at least one pension trust holds more than 25% of the value of the REIT's stock, or (b) a group of pension trusts each individually holding more than 10% of the value of the REIT's shares, collectively owns more than 50% of the value of the REIT's shares.

For pension-held REITs, the percentage of any REIT dividend treated as UBTI is equal to the ratio of the UBTI earned by the REIT, treating the REIT as if it were a pension trust and therefore subject to tax on UBTI, to the total gross income of the REIT. An exception applies, in which case no dividends are treated as UBTI, where this percentage is less than 5% for any taxable year. Before investing in our common stock, a tax-exempt stockholder should consult its tax advisors with regard to UBTI and the suitability of an investment in our common stock.

U.S. Taxation of Non-U.S. Stockholders

Distributions by AvalonBay. Distributions by us to a non-U.S. stockholder that are neither attributable to gain from sales or exchanges by us of "U.S. real property interests" nor designated by us as capital gains dividends will be treated as dividends taxed as ordinary income to the extent that they are made out of our current or accumulated earnings and profits. These distributions ordinarily will be subject to withholding of U.S. federal income tax on a gross basis at a rate of 30%, or a lower rate as permitted under an applicable income tax treaty, unless the dividends are treated as effectively connected with the conduct by the non-U.S. stockholder of a U.S. trade or business. Under some treaties, however, lower withholding rates generally applicable to dividends do not apply to dividends from REITs. Dividends that are effectively connected with a trade or business will be subject to tax on a net basis, that is, after allowance for deductions, at graduated rates, in the same manner as U.S. stockholders are taxed with respect to these dividends, and are generally not subject to withholding. Any dividends received by a corporate non-U.S. stockholder that is engaged in a U.S. trade or business also may be subject to an additional branch profits tax at a 30% rate, or lower applicable treaty rate.

Distributions in excess of our current and accumulated earnings and profits (not attributable to gains from disposition of U.S. real property interests) that exceed the non-U.S. stockholder's basis in its common stock will be taxable to a non-U.S. stockholder as gain from the sale of its common stock, which is discussed below. Distributions in excess of our current or accumulated earnings and profits (not attributable to gains from disposition of U.S. real property interests) that do not exceed the adjusted basis of the non-U.S. stockholder in its common stock will reduce the non-U.S. stockholder's adjusted basis in its common stock and will not be subject to U.S. federal income tax, but will be subject to U.S. withholding tax as described below.

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Subject to the discussion below regarding capital gain dividends and FIRPTA, we expect to withhold U.S. income tax at the rate of 30% on any dividend distributions (including distributions that later may be determined to have been in excess of current and accumulated earnings and profits) made to a non-U.S. stockholder unless:

(1): a lower treaty rate applies and the non-U.S. stockholder files an IRS Form W-8BEN evidencing eligibility for that reduced treaty rate with us; or
(2): the non-U.S. stockholder files an IRS Form W-8ECI with us claiming that the distribution is income effectively connected with such non-U.S. stockholder's trade or business within the U.S.

We may be required to withhold at least 10% of any distribution in excess of our current and accumulated earnings and profits, even if a lower treaty rate applies and the non-U.S. stockholder is not liable for tax on the receipt of that distribution. However, a non-U.S. stockholder may seek a refund of these amounts from the IRS if the non-U.S. stockholder's U.S. tax liability with respect to the distribution is less than the amount withheld.

Distributions to a non-U.S. stockholder that we designate as capital gain dividends, other than those arising from the disposition of a U.S. real property interest, generally should not be subject to U.S. federal income taxation unless:

(1): the investment in our common stock is effectively connected with the non-U.S. stockholder's U.S. trade or business, in which case the non-U.S. stockholder will be subject to the same treatment as U.S. stockholders with respect to any gain, except that a stockholder that is a foreign corporation also may be subject to the 30% branch profits tax, as discussed above; or
(2): the non-U.S. stockholder is a nonresident alien individual who is present in the U.S. for 183 days or more during the taxable year and has a "tax home" in the U.S., in which case the nonresident alien individual will be subject to a 30% tax on his or her net U.S. source capital gains.

Under the Foreign Investment in Real Property Tax Act, which is referred to as "FIRPTA," subject to the exception discussed below for 5% or smaller holders of regularly traded classes of stock, distributions to a non-U.S. stockholder that are attributable to gain from sales or exchanges by us of U.S. real property interests, whether or not designated as a capital gain dividend, will cause the non-U.S. stockholder to be treated as recognizing gain that is income effectively connected with a U.S. trade or business. The term "U.S. real property interests" includes interests in U.S. real property and shares in U.S. corporations at least 50% of whose real estate and business assets consist of U.S. real property interests. Non-U.S. stockholders will be taxed on this gain at the same rates applicable to U.S. stockholders, subject to a special alternative minimum tax in the case of nonresident alien individuals. Also, this gain may be subject to the 30% branch profits tax in the hands of a non-U.S. stockholder that is a corporation.

We will be required to withhold and remit to the IRS 35% of any distributions to non-U.S. stockholders that we designate as capital gain dividends, including any distributions that could have been designated as capital gain dividends. Distributions can be designated as capital gains to the extent of our net capital gain for the taxable year of the distribution. The amount withheld is creditable against the non-U.S. stockholder's U.S. federal income tax liability. A non-U.S. stockholder who receives distributions attributable to gain from a sale or exchange by us of U.S. real property interests will be required to file a U.S. federal income tax return for the taxable year.

A non-U.S. stockholder that owns, actually or constructively, no more than 5% of our common stock at all times during the one-year period ending on the date of the distribution will not be subject to the 35% FIRPTA withholding tax with respect to distributions that are attributable to gain from our

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sale or exchange of U.S. real property interests, provided that our common stock is regularly traded on an established securities market. Instead, any distributions made to such non-U.S. stockholder will be subject to the general withholding rules discussed above which generally impose a withholding tax equal to 30% of the gross amount of each dividend distribution (unless reduced by treaty).

Although the law is not clear on the matter, it appears that amounts designated by us as undistributed capital gains generally should be treated with respect to non-U.S. stockholders in the same manner as actual distributions by us of capital gain dividends. Under that approach, the non-U.S. stockholders would be able to offset as a credit against their U.S. federal income tax liability resulting therefrom an amount equal to their proportionate share of the tax paid by us on the undistributed capital gains, and to receive from the IRS a refund to the extent their proportionate share of this tax paid by us exceeds their actual U.S. federal income tax liability.

Sale of Common Stock. Gain recognized by a non-U.S. stockholder upon the sale or exchange of our common stock generally would not be subject to U.S. taxation unless:

(1): the investment in our common stock is effectively connected with the non-U.S. stockholder's U.S. trade or business, in which case the non-U.S. stockholder will be subject to the same treatment as U.S. stockholders with respect to any gain;
(2): the non-U.S. stockholder is a nonresident alien individual who is present in the U.S. for 183 days or more during the taxable year and has a tax home in the U.S., in which case the nonresident alien individual will be subject to a 30% tax on the individual's net capital gains for the taxable year; or
(3): our common stock constitutes a U.S. real property interest within the meaning of FIRPTA, as described below.

Our common stock will not constitute a U.S. real property interest if we are a domestically controlled qualified investment entity. We will be a domestically controlled qualified investment entity if, at all times during a specified testing period, we are a REIT and less than 50% in value of our stock is held directly or indirectly by non-U.S. stockholders.

Because our common stock is publicly traded, we cannot guarantee that we are or will continue to be a domestically controlled qualified investment entity.

Even if we are a domestically controlled qualified investment entity, upon disposition of our stock, a non-U.S. stockholder may be treated as having gain from the sale or exchange of a U.S. real property interest if the non-U.S. stockholder (1) disposes of an interest in our stock during the 30-day period preceding the ex-dividend date of a distribution, any portion of which, but for the disposition, would have been treated as gain from sale or exchange of a U.S. real property interest and (2) directly or indirectly acquires, enters into a contract or option to acquire, or is deemed to acquire, other shares of our stock within 30 days before or after such ex-dividend date. This rule does not apply if the exception for distributions to 5% or smaller holders of regularly traded classes of stock is satisfied.

Even if we do not qualify as a domestically controlled qualified investment entity at the time a non-U.S. stockholder sells its common stock, our stock sold by such stockholder would not be considered a U.S. real property interest if:

(1): the class or series of stock sold is considered regularly traded under applicable Treasury regulations on an established securities market, such as the NYSE; and
(2): the selling non-U.S. stockholder owned, actually or constructively, 5% or less in value of the outstanding class or series of stock being sold throughout the five-year period ending on the date of the sale or exchange.

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If gain on the sale or exchange of our common stock were subject to taxation under FIRPTA, a non-U.S. stockholder would be subject to regular U.S. income tax with respect to any gain in the same manner as a taxable U.S. stockholder, subject to any applicable alternative minimum tax and special alternative minimum tax in the case of nonresident alien individuals.

Other U.S. Federal Income Tax Withholding and Reporting Requirements

The Foreign Account Tax Compliance Act ("FATCA") provisions of the Code, enacted in 2010, impose withholding taxes on certain types of payments to (i) foreign financial institutions that do not agree to comply with certain diligence, reporting and withholding obligations with respect to their U.S. accounts and (ii) non-financial foreign entities that do not identify (or confirm the absence of) substantial U.S. owners. The withholding tax of 30% would apply to dividends and the gross proceeds of a disposition of our common stock paid to certain foreign entities unless various information reporting requirements are satisfied. For these purposes, a foreign financial institution generally is defined as any non-U.S. entity that (i) accepts deposits in the ordinary course of a banking or similar business, (ii) is engaged in the business of holding financial assets for the account of others, or (iii) is engaged or holds itself out as being engaged primarily in the business of investing, reinvesting, or trading in securities, partnership interests, commodities, or any interest in such assets. Withholding under this legislation on withholdable payments to foreign financial institutions and non-financial foreign entities is expected to apply after December 31, 2016 with respect to gross proceeds of a disposition of property that can produce U.S. source interest or dividends and certain other sources of income and after December 31, 2013 with respect to other withholdable payments.

Information Reporting and Backup Withholding Tax Applicable to Stockholders

U.S. Stockholders. In general, information reporting requirements will apply to payments of distributions on our common stock and payments of the proceeds of the sale of our common stock to some stockholders, unless an exception applies. Further, the payor will be required to backup withhold on any payments at the current rate of 28% if:

(1): the payee fails to furnish a taxpayer identification number, or TIN, to the payor or to establish an exemption from backup withholding;
(2): the IRS notifies the payor that the TIN furnished by the payee is incorrect; or
(3): the payee fails to certify under the penalty of perjury that the payee is not subject to backup withholding under the Code.

Some stockholders, including corporations and tax exempt organizations, will be exempt from backup withholding. Any amounts withheld under the backup withholding rules from a payment to a stockholder will be allowed as a credit against the stockholder's U.S. federal income tax and may entitle the stockholder to a refund, provided that the required information is furnished to the IRS.

Non-U.S. Stockholders. Generally, information reporting will apply to distributions on our common stock, and backup withholding at a current rate of 28% may apply, unless the payee certifies that it is not a U.S. person or otherwise establishes an exemption.

The payment of the proceeds from the disposition of our common stock to or through the U.S. office of a U.S. or foreign broker will be subject to information reporting and, possibly, backup withholding unless the non-U.S. stockholder certifies as to its non-U.S. status or otherwise establishes an exemption, provided that the broker does not have actual knowledge that the stockholder is a U.S. person or that the conditions of any other exemption are not, in fact, satisfied. The proceeds of the disposition by a non-U.S. stockholder of our common stock to or through a foreign office of a broker generally will not be subject to information reporting or backup withholding. However, if the broker is a U.S. person, a controlled foreign corporation for U.S. tax purposes or a foreign person 50% or more

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of whose gross income from all sources for specified periods is from activities that are effectively connected with a U.S. trade or business, information reporting generally will apply unless the broker has documentary evidence as to the non-U.S. stockholder's foreign status and has no actual knowledge to the contrary.

Applicable Treasury regulations provide presumptions regarding the status of stockholders when payments to the stockholders cannot be reliably associated with appropriate documentation provided to the payor. Because the application of these Treasury regulations varies depending on the stockholder's particular circumstances, you are urged to consult your tax advisor regarding the information reporting requirements applicable to you.

Other Tax Consequences for AvalonBay and its Stockholders

Our company and its stockholders may be subject to state, local and foreign tax in states, localities or foreign countries, including those in which we or they transact business or reside. The state, local and foreign tax treatment of our company and its stockholders may not conform to the U.S. federal income tax consequences discussed above. Consequently, prospective investors should consult their own tax advisors regarding the effect of state, local and foreign tax laws on an investment in our common stock. To the extent that we and our taxable REIT subsidiaries are required to pay federal, state, local or foreign taxes, we will have less cash available for distribution to stockholders.

Legislative or Other Actions Affecting REITs

The U.S. federal income tax rules are constantly under review by persons involved in the legislative process and by the IRS and the U.S. Treasury Department. No assurance can be given as to whether, when, or in what form, the U.S. federal income tax laws applicable to us and our stockholders may be enacted. Changes to the U.S. federal income tax laws and interpretations of U.S. federal income tax laws could adversely affect an investment in our common stock.

Experts

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements (and schedule) included in our Annual Report on Form 10-K for the year ended December 31, 2012, and the effectiveness of our internal control over financial reporting as of December 31, 2012, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements (and schedule) are incorporated by reference in reliance on Ernst & Young LLP's reports, given on their authority as experts in accounting and auditing.

The combined statement of revenue and certain expenses of the Archstone Portfolio for the year ended December 31, 2012, appearing in our Current Report on Form 8-K filed with the SEC on February 26, 2013, have been incorporated by reference herein in reliance upon the report of KPMG LLP, independent auditors, incorporated by reference herein, and upon authority of such firm as experts in accounting and auditing. KPMG LLP's report on the combined statement of revenue and certain expenses of the Archstone Portfolio contains a paragraph that states that the combined statement of revenue and certain expenses was prepared for the purpose of complying with the rules and regulations of the SEC, as described in Note 1 to the combined statement of revenue and certain expenses, and it is not intended to be a complete presentation of the Archstone Portfolio's revenue and expenses.

Legal Matters

The validity of the securities to be offered by this prospectus will be passed upon for us by Goodwin Procter LLP, Boston, Massachusetts.

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7,870,000 Shares

Common Stock

PROSPECTUS SUPPLEMENT

Goldman, Sachs & Co.

May 22, 2013

AvalonBay Communities (AVB) 424B5Prospectus supplement for primary offering