EXHIBIT 5.1


                                                April 21, 2004



AvalonBay Communities, Inc.
2900 Eisenhower Avenue, Suite 300
Alexandria, VA  22314

Ladies and Gentlemen:

We have acted as special counsel for AvalonBay Communities, Inc., a Maryland
corporation (the "Company"), in connection with the preparation and filing
with the Securities and Exchange Commission (the "Commission") under the
Securities Act of 1933, as amended (the "1933 Act"), of a Registration
Statement on Form S-3, as amended (File No. 333-103755) (the "Registration
Statement"), a prospectus supplement dated August 11, 2003 and a pricing
supplement dated April 14, 2004 (together, the "Prospectus Supplement"),
which supplement the prospectus included in the Registration Statement,
relating to the offering of $150,000,000 aggregate principal amount of 5.375%
Medium-Term Notes due April 15, 2014 (the "Notes") by the Company to the
Agents (as defined below) pursuant to the terms of the Amended and Restated
Distribution Agreement dated August 6, 2003 (the "Distribution Agreement") by
and among the Company and the Agents named therein (the "Agents"). The
prospectus included in the Registration Statement, as supplemented by the
Prospectus Supplement, is herein called the "Prospectus."

The Notes are to be issued pursuant to the terms of an Indenture dated as of
January 16, 1998 between the Company and U.S. Bank Trust National
Association, as successor trustee (the "Trustee"), as supplemented by the
First Supplemental Indenture dated as of January 20, 1998 between the Company
and the Trustee, the Second Supplemental Indenture dated as of July 7, 1998
between the Company and the Trustee, and the Amended and Restated Third
Supplemental Indenture dated as of July 10, 2000 between the Company and the
Trustee (collectively, the "Indenture").

We have examined the Amended and Restated Articles of Incorporation of the
Company, as amended and on file with the Maryland State Department of
Assessments and Taxation, the Amended and Restated Bylaws of the Company, the
Distribution Agreement, certified resolutions of the Board of Directors of the
Company (the "Board") and actions pursuant to authority delegated to the
Investment and Finance Committee of the Board (the "IFC Committee") authorizing
the issuance of the Notes (the "Authorizing Resolutions"), such records of
corporate proceedings of the Company and legal considerations as we have deemed
appropriate for the purposes of this opinion, the Registration Statement and the
Prospectus Supplement and the exhibits thereto. In such examination, we have
assumed the authenticity of all documents submitted to us as originals, the
conformity with the original documents of all documents submitted to us as
copies, and the accuracy of all factual statements set forth in such documents.





We are attorneys admitted to practice in The Commonwealth of Massachusetts. We
express no opinion concerning the laws of any jurisdictions other than the laws
of the United States of America, the Commonwealth of Massachusetts and the
Maryland General Corporation Law, and also express no opinion with respect to
the blue sky or securities laws of any state, including Massachusetts or
Maryland. To the extent that any other laws govern any of the matters as to
which we express an opinion herein, we have assumed, without independent
investigation, that the laws of such jurisdiction are identical to those of the
Commonwealth of Massachusetts, and we express no opinion as to whether such
assumption is reasonable or correct.

Based on the foregoing, we are of the opinion that the Notes to be sold by the
Company to or through the agents named in the Prospectus Supplement, upon
issuance in accordance with the Authorizing Resolutions and upon execution and
delivery of such Notes and payment therefore in accordance with the terms of the
Indenture and the Distribution Agreement and the related Terms Agreement dated
April 14, 2004, will be legally issued and constitute valid and binding
obligations of the Company, enforceable against the Company in accordance with
their terms and will be entitled to the benefits of the Indenture.

The foregoing opinion is qualified to the extent that the enforceability of any
document, instrument, or Note may be limited by or subject to the effects of (i)
bankruptcy, insolvency, moratorium, fraudulent conveyance or transfer,
reorganization, or other similar laws relating to or affecting creditors' rights
generally, (ii) general principles of equity or public policy principals, and
(iii) the refusal of a particular court to grant equitable remedies, including
specific performance and injunctive relief or a particular remedy sought under
the Indenture as opposed to another remedy provided for therein or available at
law or in equity. We note that the enforceability of specific provisions of the
Indenture and the Notes may be subject to (a) standards of reasonableness and
"good faith" limitations and obligations such as those provided in the Uniform
Commercial Code and similar applicable principles of common law and judicial
decisions and (b) the course of dealings between the parties, the usage of trade
and similar provisions of common law and judicial decision.

We express no opinions concerning (i) the validity or enforceability of any
provisions contained in the Indenture or Notes that purport to waive or not give
effect to rights to notice, defenses, subrogation or other rights or benefits
that cannot be effectively waived under applicable law, (ii) the enforceability
of indemnification provisions to the extent that they purport to relate to
liabilities resulting from or based on negligence or any violation of any
federal or state securities laws, (iii) the enforceability of severability
clauses or (iv) the enforceability of any provision in the Indenture or the
Notes that purports to waive liability for violation of securities laws.

The opinions expressed herein are being furnished to you solely for your benefit
in connection with the Registration Statement, and may not be used or relied
upon by you for any other purpose, nor may this opinion be quoted from,
circulated, relied upon or otherwise referred to, by any other person or entity
without our prior written consent. This opinion is given as of the date first
set forth above, and we assume no obligation to update this opinion. We hereby
consent to the use of this opinion as an exhibit to the Company's Current Report
on Form 8-K dated August 14, 2003 which is incorporated by reference into the
Registration Statement. In giving this consent, we do not admit that we are
within the category of persons whose consent is required under Section 7 of the
1933 Act or the General Rules and Regulations of the Securities and Exchange
Commission.

Very truly yours,

/s/ Goodwin Procter LLP

GOODWIN PROCTER LLP