UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 20-F

(Mark One)

OR

For the fiscal year ended December 31, 20112012

OR

For the transition period from                      to                     .

OR

Commission file number: 1-15060

UBS AG

(Exact Name of Registrant as Specified in Its Charter)

Switzerland

(Jurisdiction of Incorporation or Organization)

Bahnhofstrasse 45, CH-8001 Zurich, Switzerland

and

Aeschenvorstadt 1, CH-4051 Basel, Switzerland

(Address of Principal Executive Offices)

Sarah M. Starkweather

UBS AG

677 Washington Boulevard

Stamford, CT 06901

Telephone: (203) 719-3000

Fax: (203) 719-0680

(Name, Telephone, E-mail and/or Facsimile number and Address of Company Contact Person)

Securities registered or to be registered pursuant to Section 12(b) of the Act:

Please see page 3.

Securities registered or to be registered pursuant to Section 12(g) of the Act:

Please see page 5.

Securities for which there is a reporting obligation pursuant to Section 15(d) of the Act:

Please see page 5.

Indicate the number of outstanding shares of each of the issuer’s classes of capital or common stock as of

31 December 2011:2012:

Ordinary shares, par value CHF 0.10 per share: 3,832,121,8993,835,250,233 ordinary shares

(including 84,955,55187,879,601 treasury shares)

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.

Yes  þ            No  ¨

If this report is an annual or transition report, indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.

Yes  ¨             No  þ

Note — Checking the box above will not relieve any registrant required to file reports pursuant to

Section 13 or 15(d) of the Securities Exchange Act of 1934 from their obligations under those Sections.

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days.

Yes  þ             No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 205 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).

Yes  þ             No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check One):

Indicate by check mark which basis of accounting the registrant has used to prepare the financial statements included in this filing.

If “Other” has been checked in response to the previous question, indicate by check mark which financial statement item the registrant has elected to follow.

Item 17  ¨             Item 18  ¨

If this is an annual report, indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act)

Yes  ¨            No  þ

Securities registered or to be registered pursuant to Section 12(b) of the Act:

$100,000,000 2xMonthly Leveraged Long E-TRACS Linked to the Alerian MLP Infrastructure Index due July 9, 2040		NYSE Arca
$100,000,000 E-TRACS Linked to the Alerian Natural Gas MLP Index due July 9, 2040		NYSE Arca
$100,000,000 E-TRACS Linked to the Wells Fargo® MLP Index due October 29, 2040		NYSE Arca
$100,000,000 E-TRACS Daily Long-Short VIX ETN due November 30, 2040		NYSE Arca
$100,000,000 E-TRACS Linked to the Wells Fargo Business Development Company Index due April 26, 2041		NYSE Arca
$100,000,000 2×Leveraged Long E-TRACS Linked to the Wells Fargo® Business Development Company Index due May 24, 2041		NYSE Arca
$100,000,000 E-TRACS Oil Futures Contango ETN due June 14, 2041		NYSE Arca
$100,000,000 E-TRACS Natural Gas Futures Contango ETN due June 14, 2041		NYSE Arca
$100,000,000 E-TRACS Next Generation Internet ETN due July 19, 2041		NYSE Arca
$100,000,000 Monthly 2xLeveraged E-TRACS Next Generation Internet ETN due July 19, 2041		NYSE Arca
$100,000,000 E-TRACS Daily Short 1-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS Daily Short 2-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS Daily Short 3-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS Daily Short 4-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS Daily Short 5-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS Daily Short 6-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS 1-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS 2-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS 3-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS 4-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS 5-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca
$100,000,000 E-TRACS 6-Month S&P 500 VIX Futures ETN due September 6, 2041		NYSE Arca

$100,000,000 E-TRACS ISE Solid State Drive Index ETN due September 13, 2041		NYSE Arca
$100,000,000 E-TRACS Monthly 2xLeveraged ISE Solid State Drive Index ETN due September 13, 2041		NYSE Arca
$100,000,000 E-TRACS Monthly 2xLeveraged ISE Cloud Computing TR Index ETN due October 4, 2041		NYSE Arca
$100,000,000 E-TRACS Fisher-Gartman Risk On ETN due November 27, 2041		NYSE Arca
$100,000,000 E-TRACS Fisher-Gartman Risk Off ETN due November 27, 2041		NYSE Arca
$100,000,000 ETRACS DJ-UBS Commodity Index 2-4-6 Blended Futures ETN due April 30, 2042		NYSE Arca
$100,000,000 ETRACS Monthly Pay 2xLeveraged Dow Jones International Real Estate ETN due March 19, 2042		NYSE Arca
$100,000,000 ETRACS Monthly Pay 2xLeveraged Dow Jones Select Dividend Index ETN due May 22, 2042		NYSE Arca
$100,000,000 ETRACS Monthly Pay 2xLeveraged S&P Dividend ETN due May 22, 2042		NYSE Arca
$100,000,000 FI Enhanced Big Cap Growth ETN due June 13, 2022		NYSE Arca
$100,000,000 ETRACS Alerian MLP Index ETN due July 18, 2042		NYSE Arca
$100,000,000 ETRACS Monthly Pay 2xLeveraged Mortgage REIT ETN due October 16, 2042		NYSE Arca

Securities registered or to be registered pursuant to Section 12(g) of the Act:

None

Securities for which there is a reporting obligation pursuant to Section 15(d) of the Act:

None

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This report contains statements that constitute “forward-looking statements”, including but not limited to management’s outlook for UBS’s financial performance and statements relating to the anticipated effect of transactions and strategic initiatives on UBS’s business and future development. While these forward-looking statements represent UBS’s judgments and expectations concerning the matters described, a number of risks, uncertainties and other important factors could cause actual developments and results to differ materially from UBS’s expectations. These factors include, but are not limited to: (1) the degree to which UBS is successful in executing its announced strategic plans and related organizational changes, in particular its plans to transform its Investment Bank, its efficiency initiatives and its planned reduction in Basel III risk-weighted assets, and whether in each case those plans and changes will, when implemented, have the effects intended; (2) developments in the markets in which UBS operates or to which it is exposed, including movements in securities prices or liquidity, credit spreads, currency exchange rates and interest rates and the effect of economic conditions and market developments on the financial position or creditworthiness of UBS’s clients and counterparties; (2)(3) changes in the availability of capital and funding, including any changes in UBS’s credit spreads and ratings; (3) the ability of UBS to reduce its Basel III risk-weighted assets in order to comply with future Swiss capital requirements without materially adversely affecting its profitability; (4) changes in financial legislation and regulation in Switzerland, the US, the UK and other major financial centers which may impose constraints on or necessitate changes in the scope and location of UBS’s business activities and in its legal and booking structures, including the imposition of more stringent capital and liquidity requirements, incremental tax requirements and constraints on remuneration; (5) possible constraints or sanctions that regulatory authorities might impose on UBS, including as a consequence of the unauthorized trading incident announced in September 2011; (6), changes in UBS’s competitive position, including whether differences in regulatory capital and other requirements among the major financial centers will adversely affect UBS’s ability to compete in certain lines of business; (7)(6) the liability to which UBS may be exposed, or possible constraints or sanctions that regulatory authorities might impose on UBS, due to litigation, contractual claims and regulatory investigations, someincluding those that may arise from the ongoing investigations relating to the setting of which stemLIBOR and other benchmark rates, from the market events and losses incurred by clients and counterparties during the financial crisis of 2007-2009; (8)2007 to 2009, and from Swiss retrocessions; (7) the effects on UBS’s cross-border banking business of international tax treaties recently negotiated byor under discussion between Switzerland and other countries and future tax or regulatory developments; (9) the degree to which UBS is successful in effecting organizational changes and implementing strategic plans, and whether those changes and plans will have the effects intended; (10)(8) UBS’s ability to retain and attract the employees necessary to generate revenues and to manage, support and control its businesses; (11)businesses, which may be affected by competitive factors including compensation practices; (9) changes in accounting standards or policies, and accounting determinations or interpretations affecting the recognition of gain or loss, the valuation of goodwill and other matters; (12)(10) limitations on the effectiveness of UBS’s internal processes for risk management, risk control, measurement and modeling, and of financial models generally; (13)(11) whether UBS will be successful in keeping pace with competitors in updating its technology, particularly in trading businesses; and (14)(12) the occurrence of operational failures, such as fraud, unauthorized trading and systems failures, either within UBSfailures; and (13) the effect that these or within a counterparty.other factors or unanticipated events may have on our reputation and the additional consequences that this may have on our business and performance. Our business and financial performance could be affected by other factors identified in our past and future filings and reports, including those filed with the SEC. More detailed information about those factors is set forth in documents furnished by UBS and filings made by UBS with the SEC. UBS is not under any obligation to (and expressly disclaims any obligation to) update or alter its forward-looking statements, whether as a result of new information, future events, or otherwise.

PART I

Not required because this Form 20-F is filed as an annual report.

Not required because this Form 20-F is filed as an annual report.

A – Selected Financial Data.

Please seeSelected Financial Data on pages 440488 to 443491 andStatement of changes in equity on pages 292326 to 293327 of the Annual Report 20112012 of UBS AG (the “Annual Report”) which is annexed hereto and forms an integral part hereof.

The exchange rate for the Swiss franc as reported by the Federal Reserve System (H.10 Weekly) on 29 February 20128 March 2013 was CHF 0.90230.9535 per USD 1. See page 440488 of the Annual Report for additional exchange rate information.

Ratio of Earnings to Fixed Charges.

Please see page 443491 of the Annual Report and Exhibit 7 to this Form 20-F.

B – Capitalization and Indebtedness.

Not required because this Form 20-F is filed as an annual report.

C – Reasons for the Offer and Use of Proceeds.

Not required because this Form 20-F is filed as an annual report.

D – Risk Factors.

Please see pages 5055 to 5664 of the Annual Report.

A – History and Development of the Company

1 – 3        Please seeCorporate information on page 4637 of the Annual Report.

4              Please seeThe making of UBS on pages 1214 to 1416 andOur strategy on pages 24 to 31 of the Annual Report.

5 – 7        Not applicable.

B – Business Overview.

1,2,5,7                Please refer to pages 78 to 9 and 3035 to 4651 of the Annual Report. For a breakdown of revenues by category of activity and geographic market for each of the last three financial years, please refer to NotesNote 2a and 2b to the consolidated financial statements (the “Financial Statements”) contained in the Annual Report,,Segment reporting, on pages 319352 to 322355, and Note 2b to the Financial Statements,Segment reporting by geographic location, on page 323, respectively.356 of the Annual Report.

3 Please refer toSeasonal characteristics on page 2834 of the Annual Report.

4 Not applicable.

6 None.

8 Please seeRegulatory developments andRegulation and supervision on pages 1921 to 2123 and 4752 to 49,54, respectively, of the Annual Report.

Disclosure Pursuant To Section 219 of the Iran Threat Reduction And Syrian Human Rights Act

Section 219 of the U.S. Iran Threat Reduction and Syria Human Rights Act of 2012 (“ITRA”) added new Section 13(r) to the U.S. Securities Exchange Act of 1934, as amended (the “Exchange Act”) requiring each SEC reporting issuer to disclose in its annual and, if applicable, quarterly reports whether it or any of its affiliates have knowingly engaged in certain activities, transactions or dealings relating to Iran or with the Government of Iran or certain designated natural persons or entities involved in terrorism or the proliferation of weapons of mass destruction during the period covered by the report. The required disclosure includes disclosure of activities not prohibited by U.S. or other law even if conducted outside the U.S. by non-U.S. affiliates in compliance with local law. Pursuant to Section 13(r) of the Exchange Act, we note the following for the period covered by this annual report:

UBS AG has a Group Sanctions Policy which was implemented in 2006 that prohibits transactions involving sanctioned countries, including Iran, and sanctioned individuals and entities. However, UBS continues to maintain one account involving the Iranian government under the auspices of the United Nations in Geneva after agreeing with the Swiss government that it would do so only under certain conditions. These conditions include that payments involving the account must (1) be made within Switzerland; (2) be consistent with paying rent, salaries, telephone and other expenses necessary for its operations in Geneva; and (3) not involve any Specially Designated Nationals blocked or otherwise restricted under US or Swiss law. In 2012,the gross/net revenues for this UN related account were approximately USD 26,241 which was generated by fees charged to the account; the net profit was approximately USD 14,975 after deductions were taken for UBS internal costs for maintaining the account. UBS AG intends to continue maintaining this account pursuant to the conditions it has established and consistent with its Group Sanctions Policy.

There are also certain outstanding trade finance arrangements that had been issued on behalf of Swiss client exporters in favor of their Iranian counterparties which involve four Iranian WMD designated banks. At the time these trade finance arrangements were initiated in or about 2000, none of the Iran banks involved were WMD-designated. In February 2012, due to increasing risks involving Iran, UBS ceased accepting payments on these outstanding export trade finance arrangements. Default on such arrangements is subject to insurance by a Swiss government agency with which UBS is cooperating closely. There was no financial activity conducted in connection with these trade finance arrangements in 2012. The total exposure as a result of these outstanding arrangements is approximately USD 33,185,000 and the risk to UBS, net of Swiss government guarantees, is approximately CHF 1,659,000. There were no gross revenues or net profits for 2012.

In connection with these trade finance arrangements, UBS has maintained one existing account relationship with an Iranian bank that is currently WMD designated. This account was established as a correspondent banking relationship prior to the U.S. designation. In 2006, when UBS implemented

its Group Sanctions Policy, the relationship was closed but the account was maintained due to the existing trade finance arrangements. In or about 2007, following the designation of the bank pursuant to sanctions issued by the U.S., U.N. and Switzerland, the account was blocked under Swiss law and has remained blocked since then. Client assets as of December 2012 were USD 3,470. We intend to terminate these legacy arrangements and relationships in accordance with the nature of these instruments and applicable law. As there have been no transactions involving this account in 2012 other than general account fees, there are no gross profits/net revenues to report for 2012.

In 1993, a non-Iranian individual opened a private banking relationship at a predecessor institution of UBS AG in Switzerland. In 2001, this individual was designated under Executive Order 13224 and remains so today. In 2001, the individual’s accounts at UBS AG were blocked by order of the Swiss authorities. The Swiss authorities lifted the blocking of the individual’s UBS accounts in October 2012. UBS AG does not intend to continue this activity and has been in the process of exiting this client relationship. UBS AG has frozen the client’s remaining account until it can be closed as permitted by applicable law. In 2012, the gross revenues for this client relationship were approximately USD 184,859 and the net profit was approximately USD 141,151. These amounts reflect revenues and profits from transactions in connection with the client’s exit subsequent to the unblocking of his accounts by the Swiss authorities.

C – Organizational Structure.

Please seeUBS and its businesses on pages 8 to 9 and Note 3334 to the Financial Statements,Significant subsidiaries and associates, on pages 7 and 394441 to 397442 of the Annual Report.

D – Property, Plant and Equipment.

Please seeProperty, plant and equipment on page 444 and Notes 15 and 25492, Note 16 to the Financial Statements,Property and equipment,on page 368, and Note 26 to the Financial Statements,Operating lease commitments, on pages 335 and 358, respectively,page 395, of the Annual Report.

Information Required by Industry Guide 3

Please seeInformation required by industry guide 3 on pages 445493 to 459507 of the Annual Report. See alsoSelected financial data on pages 440488 to 443491 of the Annual Report for the return on equity attributable to UBS shareholders, return on average equity, return on average assets, dividend payout ratio and ratio of average equity to average assets.

None.There are no unresolved comments received 180 days or more before the end of the 2012 fiscal year.

A – Operating Results.

Please seeKey figureson page 6,Measurement of performanceon pages 2732 to 29,34, andUBS resultson pages 6272 to 8193 of the Annual Report. For a discussion of operating results by business division, please refer to pages 8294 to 110129 of the Annual Report.

For information regarding the impact of foreign currency fluctuations, seeCorporateInterest rate and currency management on page 152pages 172 to 173 andOur global presence subjects us to risk from currency fluctuations on pages 60 to 61 of the Annual Report. For information regarding governmental policies that could affect operations, seeCurrent market climate and industry drivers on pages 18 to 20 andRegulatory developments on pages 21 to 23 of the Annual Report.

B – Liquidity and Capital Resources.

We believe that our working capital is sufficient for the company’s present requirements. Liquidity and capital management is undertaken at UBS as an integrated asset and liability management function. For a detailed discussion, please seeLiquidity and funding managementon pages 144165 to 150171 andCapital managementon pages 153174 to 160183 of the Annual Report.

For a discussion of UBS’s borrowings and cash flows, please seeBalance sheeton pages 7284 to 7587 andCash flowson pages 8092 to 8193 of the Annual Report.

Please see alsoInterest rate and currency managementon pages 151172 to 152173 of the Annual Report, and Note 1920 to the Financial Statements,Financial liabilities designated at fair value,on pages 372 to 373 and debtNote 21 to the Financial Statements,Debt issued held at amortized cost, on pages 339373 to 340374 of the Annual Report.

C – Research and Development, Patents and Licenses, etc.

Not applicable.

D – Trend Information.

Please seeCurrent market climate and industry driverson pages 1618 to 1820 of the Annual Report.

E – Off-balance Sheet Arrangements.

Please seeOff-balance sheet arrangementson pages 7688 to 7991 of the Annual Report and Notes 24 andNote 25 to the Financial Statements,Pledgeable off-balance-sheet securitiesDerivative instruments and hedge accounting, on pages 387 to 394 and Note 26 to the Financial Statements,Operating lease commitments,respectively, on page 358395 of the Annual Report.

F – Tabular Disclosure of Contractual Obligations.

Please seeContractual obligationson page 7991 of the Annual Report.

A – Directors and Senior Management.

1,2,3 Please see page 5, pages 204230 to 208234 and pages 212239 to 216242 of the Annual Report.

4, 5 None.

B – Compensation.

1 Please see pages 268300 to 278312 of the Annual Report and also Note 3031 to the Financial Statements,Equity participation and other compensation plans, on pages 381428 to 390437 and Note 3132 to the Financial Statements,Related parties, on pages 391438 to 393440 of the Annual Report.

2 Please see Note 2930 to the Financial Statements,Pension and other post-employment benefit plans, on pages 375416 to 380427 of the Annual Report.

C – Board practices.

1 Please see pages 204230 to 219246 of the Annual Report.

2 Please see pages 272306 to 278312 of the Annual Report and Note 3132 to the Financial Statements,Related parties, on pages 391438 to 393440 of the Annual Report.

3 Please seeAudit committee andHuman Resources and Compensation Committeeon pages 209235 to 210236 of the Annual Report.

D—Employees.

Please seeOur employeeson pages 234263 to 239269 of the Annual Report.

E—Share Ownership.

Please see pages 273307 to 277311 in the Annual Report, Note 3031 to the Financial Statements,Equity participation and other compensation plans,on pages 381428 to 390437 of the Annual Report and “Equity holdings” in Note 3132 to the Financial Statements,Related parties,on page 391438 of the Annual Report.

A—Major Shareholders.

Please seeGroup structure and shareholderson pages 197223 to 198224 of the Annual Report. The number of shares held by the respective shareholders listed in the “Shareholders registered in the UBS share register with 3% or more of shares issued” table on page 197223 is as follows:

The listed shareholders have the samePlease see Transferability, voting rights as other shareholdersand nominee registration on page 227 of UBS.the Annual Report for information about certain restrictions on the rights of the listed shareholders.

At December 31, 2011,2012, the portion of UBS ordinary shares held in the United States was 265,029,075436,853,595 by 1,2299,228 record holders.

B—Related Party Transactions.

Please seeLoanson page 269303 of the Annual Report, Note 3132 to the Financial Statements,Related parties,on pages 391438 to 393440 of the Annual Report andLoans granted to BoD members on 31 December 2010/20112011/2012andLoans granted to GEB members on 31 December 2010/20112011/2012 on page 278312 of the Annual Report.

The aforementioned loans (a) were made in the ordinary course of business, (b) were made on substantially the same terms, including interest rates and collateral, as those prevailing at the time for comparable transactions with other persons, and (c) did not involve more than the normal risk of collectability or present other unfavorable features.

C—Interests of Experts and Counsel.

Not applicable because this Form 20-F is filed as an annual report.

Item 8.

Financial Information.

A—Consolidated Statements and Other Financial Information.

1, 2, 3, 4, 5, 6 Please see Item 18 of this Form 20-F.

7 Information on material legal and regulatory proceedings is in Note 2123 to the Financial Statements,Provisions and contingent liabilities, on pages 341375 to 348384 of the Annual Report. For developments during the year, please see also Note 15,the noteProvisions and contingent liabilities, in the Financial Information section in each of our quarterly reports: First Quarter 20112012 Report, filed on Form 6-K dated April 26, 2011;May 2, 2012 (Note 16); Second Quarter 20112012 Report, filed on Form 6-K dated July 26, 2011;31, 2012 (Note 16); Third Quarter 20112012 Report, filed on Form 6-K dated October 25, 2011;30, 2012 (Note 17); and Fourth Quarter 20112012 Report, filed on Form 6-K dated February 7, 2012.5, 2013 (Note 16). The Notes in each such Quarterly Report speak only as of their respective dates.

8 Please refer toDistributions to shareholderson page 159182 of the Annual Report for a description of UBS’s dividend policy.

B—Significant Changes.

UBS is not aware of any significant change that has occurred since the date of the annual financial statements included in this Form 20-F. Please see Note 321 to the Financial Statements,Summary of significant accounting policies, on pages 331 to 351, Note 2a to the Financial Statements,Segment reporting, on pages 352 to 355, and Note 33 to the Financial Statements,Events after the reporting period,on pages 393 to 394page 440 of the Annual Report.Report.

A – Offer and Listing Details.

1,2,3,5,6,7 Not required because this Form 20-F is filed as an annual report.

4         Please seeStock exchange prices on page 183 of the Annual Report.

B—Plan of Distribution.

Not required because this Form 20-F is filed as an annual report.

C—Markets.

UBS’s shares are listed and traded on the SIX Swiss Exchange and the New York Stock Exchange. The symbols are shown on page 461509 of the Annual Report.

D—Selling Shareholders.

Not required because this Form 20-F is filed as an annual report.

E—Dilution.

Not required because this Form 20-F is filed as an annual report.

F—Expenses of the Issue.

Not required because this Form 20-F is filed as an annual report.

Item 10.

Additional Information.

A—Share Capital.

Not required because this Form 20-F is filed as an annual report.

B—Memorandum and Articles of Association.

Please see the Articles of Association of UBS AG and the Organization Regulations of UBS AG (Exhibits 1.1 and 1.2, respectively, ofto this Form 20-F).

Set forth below is a summary of the material provisions of our Articles of Association, which we call the “Articles” throughout this document, Organization Regulations and the Swiss Code of Obligations relating to our shares. This description does not purport to be complete and is qualified in its entirety by references to Swiss law, including Swiss company law, and to the Articles and Organization Regulations.

The shares are registered shares with a par value of CHF 0.10 per share. The shares are fully paid up.

Each share carries one vote at our shareholders’ meetings. Voting rights may be exercised only after a shareholder has been recorded in our share register as a shareholder with voting rights. Registration with voting rights is subject to certain restrictions. See “— Transfer of Shares” and “—Shareholders’ Meeting”.

The Articles provide that we may elect not to print and deliver certificates in respect of registered shares. Shareholders may, however, following registration in the share register, request at any time that we issue a written statement in respect of their shares.

For information regarding the Board of Directors, seeElections and terms of office andOrganizational principles and structure on pages 235 to 237 of the Annual Report.

Transfer of Shares

The transfer of shares is effected by corresponding entry in the books of a bank or depository institution following an assignment in writing by the selling shareholder and notification of such assignment to us by the bank or depository institution. The transfer of shares further requires that the purchaser file a share registration form in order to be registered in our share register as a shareholder. Failing such registration, the purchaser may not vote at or participate in shareholders’ meetings.

A purchaser of shares will be recorded in our share register with voting rights upon disclosure of its name, citizenship and address. However, we may decline a registration with voting rights if the shareholder does not declare that it has acquired the shares in its own name and for its own account. If the shareholder refuses to make such declaration, it will be registered as a shareholder without voting rights.

There is no limitation under Swiss law or our Articles on the right of non-Swiss residents or nationals to own or vote our shares.

Shareholders’ Meeting

Under Swiss law, annual ordinary shareholders’ meetings must be held within six months after the end of our financial year, which is 31 December. Shareholders’ meetings may be convened by the Board of Directors (BoD) or, if necessary, by the statutory auditors, with twenty-days’ advance notice. The BoD is further required to convene an extraordinary shareholders’ meeting if so resolved by a shareholders’ meeting or if so requested by shareholders holding in aggregate at least 10% of our nominal share capital. Shareholders holding shares with an aggregate par value of at least CHF 62,500 have the right to request that a specific proposal be put on the agenda and voted upon at the next shareholders’ meeting. A shareholders’ meeting is convened by publishing a notice in the Swiss Official Commercial Gazette (Schweizerisches Handelsamtsblatt) at least twenty days prior to such meeting.

The Articles do not require a minimum number of shareholders to be present in order to hold a shareholders’ meeting.

Resolutions generally require the approval of an “absolute majority” of the votes cast at a shareholders’ meeting. Shareholders’ resolutions requiring a vote by absolute majority include:

Under the Articles, a resolution passed at a shareholders’ meeting with a supermajority of at least two thirds of the Shares represented at such meeting is required to:

Under Swiss corporate law, a resolution passed by at least two thirds of votes represented and an absolute majority of the par value of the shares represented must approve:

At shareholders’ meetings, a shareholder can be represented by his or her legal representative or under a written power of attorney by another shareholder eligible to vote, by a corporate proxy, by the independent proxy or by a custodial proxy. Votes are taken electronically, by written ballot or by a show of hands. If a written ballot is requested by at least 3% of the votes present at the shareholders’ meeting or such ballot is ordered by the Chairman of the meeting, a written ballot will be conducted.

Net Profits and Dividends

Swiss law requires that at least 5% of the annual net profits of a corporation must be retained as general reserves for so long as these reserves amount to less than 20% of the corporation’s nominal share capital. Any net profits remaining are at the disposal of the shareholders’ meeting, except that, if an annual dividend exceeds 5% of the nominal share capital, then 10% of such excess must be retained as general reserves.

Under Swiss law, dividends may be paid out only if the corporation has sufficient distributable profits from previous business years or if the reserves of the corporation are sufficient to allow distribution of a dividend. In either event, dividends may be paid out only after approval by the shareholders’ meeting. The BoD may propose to the shareholders that a dividend be paid out, but cannot itself set the dividend.out. The auditors must confirm that the dividend proposal of the Board conforms with statutory law. In practice, the shareholders’ meeting usually approves the dividend proposal of the BoD.

Dividends are usually due and payable after the shareholders’ resolution relating to the allocation of profits has been passed. Under Swiss law, the statuestatute of limitations in respect of dividend payments is five years.

U.S. holders of shares will receive dividend payments in U.S. dollars, unless they provide notice to our U.S. transfer agent, BNY Mellon Shareowner Services,Computershare, that they wish to receive dividend payments in Swiss francs. The U.S. transfer agent will be responsible for paying the U.S. dollars or Swiss francs to registered holders, and for withholding any required amounts for taxes or other governmental charges. If the U.S. transfer agent determines, after consultation with us, that in its judgment any foreign currency received by it cannot be converted into U.S. dollars or transferred to U.S. holders, it may distribute the foreign currency received by it, or an appropriate document evidencing the right to receive such currency, or in its discretion hold such foreign currency for the accounts of U.S. holders.

Preemptive Rights

Under Swiss law, any share issue, whether for cash or non-cash consideration or for no consideration, is subject to the prior approval of the shareholders’ meeting. Shareholders of a Swiss corporation have certain preemptive rights to subscribe for new issues of shares in proportion to the nominal amount of shares held. The Articles or a resolution adopted at a shareholders’ meeting with a supermajority may, however, limit or suspend preemptive rights in certain limited circumstances.

Borrowing Power

Neither Swiss law nor the Articles restrict in any way our power to borrow and raise funds. No shareholders’ resolution is required.

Conflicts of Interests

Swiss law does not have a general provision on conflicts of interests. However, the Swiss Code of Obligations requires directors and members of senior management to safeguard the interests of the corporation and, as such, imposes a duty of care and a duty of loyalty on directors and officers. This rule is generally understood as disqualifying directors and senior officers from participating in

decisions that directly affect them. Directors and officers are personally liable to the corporation for any breach of these provisions. In addition, Swiss law contains a provision under which payments made to a shareholder or a director or any person associated therewith, other than at arm’s length, must be repaid to us if the shareholder or director was acting in bad faith.

In addition, our Organization Regulations prohibit any member of the BoD from participating in discussions and decision-making regarding a matter as to which he or she has a conflict of interest.

Repurchase of Shares

Swiss law limits a corporation’s ability to hold or repurchase its own shares. We and our subsidiaries may only repurchase shares if we have sufficient free reserves to pay the purchase price and if the aggregate nominal value of the shares does not exceed 10% of our nominal share capital. Furthermore, we must create a special reserve on our balance sheet in the amount of the purchase price of the acquired shares. Such shares held by us or our subsidiaries do not carry any rights to vote at shareholders’ meetings.

Notices

Notices to shareholders are made by publication in the Swiss Official Gazette of Commerce. The BoD may designate further means of communication for publishing notices to shareholders.

Notices required under the listing rules of the SIX Swiss Exchange will be published in two Swiss newspapers in German and French. We or the SIX Swiss Exchange may also disseminate the relevant information on the online exchange information systems.

Registration and Business Purpose

We are registered as a corporation in the commercial registers of Canton Zurich and Canton Basle-City under the registration number CH-270.3.004.646-4 and have registered offices in Zurich and Basel, Switzerland.

Our business purpose, as set forth in our Articles, is the operation of a bank, with a scope of operations extending to all types of banking, financial, advisory, trading and service activities in Switzerland and abroad.

Duration, Liquidation and Merger

Our duration is unlimited.

Under Swiss law, we may be dissolved at any time by a shareholders’ resolution which must be passed by (1) an absolute majority of the shares represented at the meeting in the event we are to be dissolved by way of liquidation, or (2) a supermajority of at least two thirds of the votes represented and an absolute majority of the par value of the shares represented at the meeting in other events (for example, in a merger where we are not the surviving entity). Dissolution by court order is possible if we become bankrupt.

Under Swiss law, any surplus arising out of a liquidation (after the settlement of all claims of all creditors) is distributed to shareholders in proportion to the paid-up nominal value of shares held.

Disclosure of Principal Shareholders

Under the applicable provisions of the new Swiss Stock Exchange Act, shareholders and shareholders acting in concert with third parties who reach, exceed or fall below the thresholds of 3%, 5%, 10%, 15%, 20%, 25%, 33 1/3%, 50% or 66 2/3% of the voting rights of a Swiss listed corporation must notify the corporation and the SIX Swiss Exchange on which such shares are listed of such holdings, whether or not the voting rights can be exercised. Following receipt of such notification, the corporation has the obligation to inform the public. The corporation must disclose in an attachment to the balance sheet the identity of any shareholders who own in excess of 5% of its shares.

Mandatory Tender Offer

Under the Swiss Stock Exchange Act, shareholders and groups of shareholders acting in concert who acquire more than 33 1/3% of the voting rights of a listed Swiss company will have to submit a takeover bid to all remaining shareholders. A waiver from the mandatory bid rule may be granted by our supervisory authority. If no waiver is granted, the mandatory takeover bid must be made pursuant to the procedural rules set forth in the Swiss Stock Exchange Act and implementing ordinances.

Other

Ernst & Young Ltd, Aeschengraben 9, CH-4051 Basel, Switzerland, have been appointed as statutory auditors and as auditors of the consolidated accounts of UBS. The auditors are subject to confirmation by the shareholders at the ordinary general meeting on an annual basis.

Please seeCapital structureon pages 199225 to 201,227,Shareholders’ participation rightson pages 202228 to 203229 andElectionsElection and terms of officeon page 208235 of the Annual Report.

C—Material Contracts.

The Fiscal Agency AgreementAgreements related to the loss-absorbing tier 2 notenotes issued on 22 February 2012 and 17 August 2012 are filed herewith as exhibits. Please see the description of these notes underBasel 2.5 tier 2 capital on pages 176 to 177 of the Annual Report.

The Non-Prosecution Agreement that UBS entered into with the US Department of Justice on December 18, 2012, is filed herewith as an exhibit. Please see the description of this note underagreement in paragraph 13 of Note 23b to the Financial Statements,Tier 2 capitalLitigation, regulatory and similar matters, on page 156pages 382 to 383 of the Annual Report.Report

D—Exchange Controls.

There are no restrictions under UBS’s Articles of Association or Swiss law, presently in force, that limit the right of non-resident or foreign owners to hold UBS’s securities freely. There are currently no Swiss foreign exchange controls or other Swiss laws restricting the import or export of capital by UBS or its subsidiaries. In addition, there are currently no restrictions under Swiss law affecting the remittance of dividends, interest or other payments to non-resident holders of UBS securities.

E—Taxation.

This section outlines the material Swiss tax and U.S. federal income tax consequences of the ownership of UBS ordinary shares by a U.S. holder (as defined below) who holds UBS ordinary shares as capital assets. It is designed to explain the major interactions between Swiss and U.S. taxation for U.S. persons who hold UBS shares.

The discussion does not address the tax consequences to persons who hold UBS ordinary shares in particular circumstances, such as tax-exempt entities, banks, financial institutions, life insurance

companies, broker-dealers, traders in securities that elect to use a mark-to-market method of accounting for securities holdings, holders liable for alternative minimum tax, holders that actually or constructively own 10% or more of the voting stock of UBS, holders that hold UBS ordinary shares as part of a straddle or a hedging or conversion transaction, holders that purchase or sell ordinary shares as part of a wash sale for tax purposes or holders whose functional currency for U.S. tax purposes is not the U.S. dollar. This discussion also does not apply to holders who acquired their UBS ordinary shares through a tax-qualified retirement plan, nor generally to unvested UBS ordinary shares held under deferred compensation arrangements.

If a partnership holds UBS ordinary shares, the U.S. federal income tax treatment of a partner will generally depend on the status of the partner and the tax treatment of the partnership. A partner in a partnership holding the ordinary shares should consult its tax advisor with regard to the U.S. federal income tax treatment of an investment in the ordinary shares.

The discussion is based on the tax laws of Switzerland and the United States, including the U.S. Internal Revenue Code of 1986, as amended, its legislative history, existing and proposed regulations under the Internal Revenue Code, published rulings and court decisions, as in effect on the date of this document, as well as the Convention between the United States of America and the Swiss Confederation for the Avoidance of Double Taxation with Respect to Taxes on Income, which we call the “Treaty,” all of which may be subject to change or change in interpretation, possibly with retroactive effect.

For purposes of this discussion, a “U.S. holder” is any beneficial owner of UBS ordinary shares that is for U.S. federal income tax purposes:

The discussion does not generally address any aspects of Swiss taxation other than income and capital taxation or of U.S. taxation other than federal income taxation. Holders of UBS shares are urged to consult their tax advisors regarding the U.S. federal, state and local and the Swiss and other tax consequences of owning and disposing of these shares in their particular circumstances.

(a) Ownership of UBS Ordinary Shares-Swiss Taxation

Dividends and Distributions

Dividends paid by UBS to a holder of UBS ordinary shares (including dividends on liquidation proceeds and stock dividends) are in principle subject to a Swiss federal withholding tax at a rate of 35%.

Until the end of 2010, the Par Value Principle was applicable. Under the Par Value Principle any distribution, which was not a repayment of the par value of the shares, was subject to Swiss withholding tax.

On 1 January 2011, the Par Value Principle was replaced by the Capital Contribution Principle. Under the Capital Contribution Principle, the repayment of capital contributions, including share premiums made by the shareholders after December 31, 1996 is in principle no longer subject to Swiss withholding tax if certain requirements regarding the booking of these capital contributions are met. The Swiss Federal Tax Administration issued guidelines on how the Capital Contribution Principle has to be applied. Nevertheless certain aspects are still unclear and disputed respectively.

A U.S. holder that qualifies for Treaty benefits may apply for a refund of the withholding tax withheld in excess of the 15% Treaty rate (or for a full refund in case of qualifying retirement arrangements). The claim for refund must be filed with the Swiss Federal Tax Administration, Eigerstrasse 65, CH-3003 Berne, Switzerland no later than December 31 of the third year following the end of the calendar year in which the income subject to withholding was due. The form used for obtaining a refund is Swiss Tax Form 82 (82 C for companies; 82 E for other entities; 82 I for individuals; 82 R for regulated investment companies), which may be obtained from any Swiss Consulate General in the United States or from the Swiss Federal Tax Administration at the address above. The form must be filled out in triplicate with each copy duly completed and signed before a notary public in the United States. The form must be accompanied by evidence of the deduction of withholding tax withheld at the source.

BNY Mellon Shareowner Services, the registrar for UBS AG shares in the United States, is offering tax reclamation services for the cash dividends.

Transfers of UBS Ordinary Shares

The purchase or sale of UBS ordinary shares, whether by Swiss resident or non-resident holders (including U.S. holders), may be subject to a Swiss securities transfer stamp duty of up to 0.15% calculated on the purchase price or sale proceeds if it occurs through or with a bank or other securities dealer in Switzerland as defined in the Swiss Federal Stamp Tax Act in Switzerland or the Principality of Liechtenstein. In addition to the stamp duty, the sale of UBS ordinary shares by or through a member of a recognized stock exchange may be subject to a stock exchange levy.

Capital gains realized by a U.S. holder upon the sale of UBS ordinary shares are not subject to Swiss income or gains taxes, unless such U.S. holder holds such shares as business assets of a Swiss business operation qualifying as a permanent establishment for the purposes of the Treaty. In the latter case, gains are taxed at ordinary Swiss individual or corporate income tax rates, as the case may be, and losses are deductible for purposes of Swiss income taxes.

(b) Ownership of UBS Ordinary Shares-U.S. Federal Income Taxation

Dividends and Distributions

Subject to the passive foreign investment company rules discussed below, U.S. holders will include in gross income the gross amount of any dividend paid, before reduction for Swiss withholding taxes, by UBS out of its current or accumulated earnings and profits, as determined for U.S. federal income tax purposes, as ordinary income when the dividend is actually or constructively received by the U.S. holder. Distributions in excess of current and accumulated earnings and profits, as determined for U.S. federal income tax purposes, will be treated as a return of capital to the extent of the U.S. holder’s basis in its UBS ordinary shares and thereafter as capital gain.

Dividends paid to a noncorporate U.S. holder in taxable years beginning before January 1, 2013 that constitute qualified dividend income will be taxable to the holder at a maximum rate of 15%20%, provided that the holder has a holding period in the shares of more than 60 days during the 121-day period beginning 60 days before the ex-dividend date and meets other holding period requirements. Dividends paid by UBS with respect to the shares will generally be qualified dividend income.

For U.S. federal income tax purposes, a dividend will include a distribution characterized under Swiss law as a repayment of capital contributions if the distribution is made out of current or accumulated earnings and profits, as described above.

Dividends will generally be income from sources outside the United States for foreign tax credit limitation purposes, and will, depending on the holder’s circumstances, be either “passive” or “general” income for purposes of computing the foreign tax credit allowable to the holder. Special

rules apply in determining the foreign tax credit limitation with respect to dividends that are subject to the maximum 15%20% rate. The dividend will not be eligible for the dividends-received deduction generally allowed to U.S. corporations in respect of dividends received from other U.S. corporations.

The amount of the dividend distribution included in income of a U.S. holder will be the U.S. dollar value of the Swiss franc payments made, determined at the spot Swiss franc/U.S. dollar rate on the date such dividend distribution is includible in the income of the U.S. holder, regardless of whether the payment is in fact converted into U.S. dollars. Generally, any gain or loss resulting from currency exchange fluctuations during the period from the date the dividend distribution is included in income to the date such dividend distribution is converted into U.S. dollars will be treated as ordinary income or loss and will not be eligible for the special tax rate applicable to qualified dividend income. Such gain or loss will generally be income or loss from sources within the United States for foreign tax credit limitation purposes.

Subject to U.S. foreign tax credit limitations, the nonrefundable Swiss tax withheld and paid over to Switzerland will be creditable or deductible against the U.S. holder’s U.S. federal income tax liability. To the extent a refund of the tax withheld is available to a U.S. holder under the laws of Switzerland or under the Treaty, the amount of tax withheld that is refundable will not be eligible for credit against the U.S. holder’s U.S. federal income tax liability, whether or not the refund is actually obtained. See “(a) Ownership of UBS Ordinary Shares – Swiss Taxation” above, for the procedures for obtaining a tax refund.

Transfers of UBS Ordinary Shares

Subject to the passive foreign investment company rules discussed below, a U.S. holder that sells or otherwise disposes of UBS ordinary shares generally will recognize capital gain or loss for U.S. federal income tax purposes equal to the difference between the U.S. dollar value of the amount realized and the tax basis, determined in U.S. dollars, in the UBS ordinary shares. Capital gain of a non-corporate U.S. holder is generally taxed at preferential rates if the UBS ordinary shares were held for more than one year. The gain or loss will generally be income or loss from sources within the United States for foreign tax credit limitation purposes.

Passive Foreign Investment Company Rules

UBS believes that UBS ordinary shares should not be treated as stock of a passive foreign investment company for U.S. federal income tax purposes, but this conclusion is a factual determination made annually and thus may be subject to change. In general, UBS will be a passive foreign investment company with respect to a U.S. holder if, for any taxable year in which the U.S. holder held UBS ordinary shares, either (i) at least 75% of the gross income of UBS for the taxable year is passive income or (ii) at least 50% of the value, determined on the basis of a quarterly average, of UBS’s assets is attributable to assets that produce or are held for the production of passive income (including cash). If UBS were to be treated as a passive foreign investment company, then unless a U.S. holder were to make a mark-to-market election with respect to the UBS ordinary shares, gain realized on the sale or other disposition of UBS ordinary shares would in general not be treated as capital gain. Instead, a U.S. holder would be treated as if the holder had realized such gain and certain “excess distributions” ratably over the three preceding taxable years or, if shorter, the holder’s holding period for the shares and would be taxed at the highest tax rate in effect for each such year to which the gain was allocated, together with an interest charge in respect of the tax attributable to each such year. With certain exceptions, a holder’s UBS ordinary shares will be treated as stock in a passive foreign investment company if UBS was a passive foreign investment company at any time during the holder’s holding period in the UBS ordinary shares. In addition, dividends received from UBS would not be eligible for the preferential tax rate applicable to qualified dividend income if UBS were to be treated as a passive foreign investment company either in the taxable year of the distribution or the preceding taxable year, but would instead be taxable at rates applicable to ordinary income.

F—Dividends and Paying Agents.

Not required because this Form 20-F is filed as an annual report.

G—Statement by Experts.

Not required because this Form 20-F is filed as an annual report.

H—Documents on Display.

UBS files periodic reports and other information with the Securities and Exchange Commission. You may read and copy any document that we file with the SEC on the SEC’s website, www.sec.gov, or at the SEC’s public reference room at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 (in the United States) or at +1 202 942 8088 (outside the United States) for further information on the operation of its public reference room. Much of this additional information may also be found on the UBS website at www.ubs.com/investors.

I—Subsidiary Information.

Not applicable.

(a) Quantitative Information About Market Risk.

Please seeMarket riskon pages 133154 to 139160 of the Annual Report.

(b) Qualitative Information About Market Risk.

Please seeMarket riskon pages 133154 to 139160 of the Annual Report.

(c) Interim Periods.

Not applicable.

A – Debt Securities

Not required because this Form 20-F is filed as an annual report.

B – Warrants and Rights

Not required because this Form 20-F is filed as an annual report.

C – Other Securities

Not required because this Form 20-F is filed as an annual report.

D – American Depositary Shares

1,2 Not required because this Form 20-F is filed as an annual report.

3,4 Not applicable.

PART II

There has been no material default in respect of any indebtedness of UBS or any of its significant subsidiaries or any arrearages of dividends or any other material delinquency not cured within 30 days relating to any preferred stock of UBS AG or any of its significant subsidiaries.

Not applicable.None.

(a) Disclosure Controls and Procedures.Procedures

Please seeUS regulatoryU.S. Regulatory disclosure requirementson page 221248 of the Annual Report. See also Exhibit 12 to this Form 20-F.

(b) Management’s Annual Report on Internal Control over Financial Reporting.Reporting

Please seeManagement’s Report on Internal Control over Financial Reportingon page 284pages 317 to 318 of the Annual Report.

(c) Attestation Report of the Registered Public Accounting Firm.Form

Please seeReport of independent registered public accounting firm on internal control over financial reporting on pages 285319 to 286320 of the Annual Report.

(d) Changes in Internal Control over Financial Reporting.Reporting

Please seeUpdate on internalRemediation of identified control over financial reportingdeficiencies on page 283pages 317 to 318 of the Annual Report for a discussion of changes in UBS’s internal control over financial reporting identified in connection with the evaluation of such controls described therein.made during 2012.

Not applicable.

Please seeAudit committeeon page 209pages 235 to 236 andCorporate governanceon page 196222 of the Annual Report.

TheThere was no substantive amendment to the Code of Business Conduct and Ethics (the “Code”) was not amended in 2011.2012, although minor updating changes were made. No waiver from any provision of the Code was granted to any employee in 2011.2012.

The Code is published on our website underhttp://www.ubs.com/1/e/investors/corporategovernance/business_conduct.html.business_conduct.html.

Item 16C.  Principal Accountant Fees and Services.

Please seeAuditorson pages 218245 to 219246 of the Annual Report. None of the non-audit services disclosed in the table on page 219245 were approved by the Audit Committee pursuant to paragraph (c) (7)(i)(C ) of Rule 2-01 of Regulation S-X.

Item 16D.  Exemptions from the Listing Standards for Audit Committees.

Not applicable.

Item 16E.  Purchases of Equity Securities by the Issuer and Affiliated Purchasers.

Please seeTreasury share activitieson page 159181 of the Annual Report.

Item 16F.  Changes in Registrant’s Certifying Accountant.

Not applicable.

Item 16G.  Corporate Governance.

Please seeCorporate governance on page 196222 of the Annual Report.

PART III

Not applicable.

Please see the Financial Statements and the Notes to the Financial Statements on pages 280314 to 410455 of the Annual Report.

SIGNATURES

The registrant hereby certifies that it meets all of the requirements for filing on Form 20-F and that it has duly caused the undersigned to sign this annual report on its behalf.

March 15, 201214, 2013

INDEX TO EXHIBITS

			Annual Report 20112012

Ourperformancein 20112012

   Contents

Annual Report 20112012

Letter to shareholders

Dear shareholders,

¹   The term “dividend” is used throughout the report, notwithstanding that for Swiss tax purposes the distribution is characterized as a payment from capital contribution reserves. Refer to the “Statement of appropriation of retained earnings” of the Parent Bank in the “Financial information” section of this report for more information.  ²  Our pro formapro-forma Basel III risk-weighted assetsinformation is not required to be presented because Basel III requirements were not in effect on 31 December 2012. Such measures are non-GAAP financial measures as defined by SEC regulations. We nevertheless include information on the basis of Basel III requirements because they are effective as of 1 January 2013 and significantly impact our RWA and eligible capital. The calculation is a combination of theour pro-forma Basel III RWA combines existing Basel 2.5 risk-weighted assets,RWA, a revised treatment for low-rated securitization exposures which applies a fixed risk weighting, as well as severalthat are no longer deducted from capital but are risk-weighted at 1250%, and new model-based capital charges which require the developmentcharges. Some of these new models require final regulatory approval and calculation engines. Our pro forma Basel III risk-weighted assets are based ontherefore our pro-forma calculations include estimates (discussed with our primary regulator) of the impacteffect of these new capital charges andwhich will be refined as we progress with our implementationmodels and the associated systems are enhanced.

Axel A. Weber Chairman of the new models and associated systems.

Board of Directors        Sergio P. Ermotti Group Chief Executive Officer        Kaspar Villiger Chairman of the Board of Directors

Annual Report 20112012

Letter to shareholders

In September,

Annual Report 20112012

Key figures

¹  Refer to “Note 8 Earnings per share (EPS) and shares outstanding” in the “Financial information” section of this report for more information.  ²  For the definitions of our key performance indicators, refer to the “Measurement of performance” section of this report.  ³  Net profit attributable to UBS shareholders before amortization and impairment of goodwill and intangible assets / average equity attributable to UBS shareholders less average goodwill and intangible assets.  ⁴  Based on Basel 2.5 risk-weighted assets for 2012. Based on Basel II risk-weighted assets for 2011 and 2010.  ⁵Not meaningful and not included if either the reporting period or the comparison period is a loss period.  ⁴⁶  ExcludesGroup net new money includes net new money for Retail & Corporate and excludes interest and dividend income.  ⁵⁷  Capital management data as of 31 December 2011 is disclosed in accordance with the Basel 2.5 framework. Comparative data under the new framework is not available for 31 December 20102012 and 31 December 2009. The comparative information under2011, and in accordance with the Basel II framework is therefore provided.for 31 December 2010. Refer to the “Capital management” section of this report for more information.  ⁶⁸  Refer to the “Capital management” section of this report for more information.  ⁷⁹  In 2012, we refined our definition of invested assets. Refer to “Note 35 Invested assets and net new money” in the “Financial information” section of this report for more information. Group invested assets includes invested assets for Retail & Corporate.  ¹⁰  Refer to the appendix “UBS registered shares” inof this report for more information.

The 2011 results and the balance sheet in this report differ from those presented in our fourth quarter 2011 report issued on 7 February 2012. The net impact of adjustments made subsequent to the publication of the unaudited fourth quarter 2011 financial report on net profit attributable to UBS shareholders was a loss of CHF 74 million, which decreased basic and diluted earnings per share by CHF 0.02.

Corporate information

Annual Report 2012

UBS and its businesses

We draw on our 150-year heritage to serve private, institutional and corporate clients worldwide, as well as retail clients in Switzerland. Our business strategy is centered on our pre-eminent global wealth management businesses and our leading universal bank in Switzerland. Together with a client-focused Investment Bank and a strong, well-diversified Global Asset Management business, we will drive further growth and expand our premier wealth management franchise.franchise and drive further growth across the Group. Headquartered in Zurich and Basel, Switzerland, we have offices in more than 50 countries, including all major financial centers, and employ approximately 65,000 people.63,000 employees. UBS AG is the parent company of the UBS Group (Group). Under Swiss company law, we areUBS AG is organized as an Aktiengesellschaft, (AG), a corporation that has issued shares of common stock to investors. UBS AG is the parent company of the UBS Group (Group). The operational structure of the Group comprises the Corporate Center and fourfive business divisions: Wealth Management, & Swiss Bank, Wealth Management Americas, the Investment Bank, Global Asset Management and the Investment Bank.Retail & Corporate.

Annual Report 2011

Our Board of Directors

¹Kaspar Villiger Chairman of the Board of Directors, Chairperson of the Governance and Nominating Committee and member of the Corporate Responsibility Committee  ²Michel DemaréIndependent Vice Chairman, member of the Audit Committee and the Governance and Nominating Committee  ³David Sidwell Senior Independent Director, Chairperson of the Risk Committee and member of the Governance and Nominating Committee  ⁴Rainer-Marc Frey Member of the Audit Committee and the Risk Committee  ⁵Bruno Gehrig Member of the Governance and Nominating Committee and the Human Resources and Compensation Committee  ⁶Ann F. Godbehere Chairperson of the Human Resources and Compensation Committee, member of the Audit Committee and the Corporate Responsibility Committee  ⁷Axel P. Lehmann Member of the Governance and Nominating Committee and the Risk Committee  ⁸Wolfgang Mayrhuber Chairperson of the Corporate Responsibility Committee and member of the Human Resources and Compensation Committee  ⁹Helmut Panke Member of the Human Resources and Compensation Committee, member of the Risk Committee  ¹⁰William G. Parrett of Chairperson of the Audit Committee  ¹¹Joseph Yam Member of the Corporate Responsibility Committee and the Risk Committee

Annual Report 2011

Our Group Executive Board

¹Sergio P. Ermotti Group Chief Executive Officer  ²Markus U. Diethelm Group General Counsel  ³John A. Fraser Chairman and CEO Global Asset Management  ⁴Lukas Gähwiler CEO UBS Switzerland and co-CEO Wealth Management & Swiss Bank  ⁵Carsten Kengeter Chairman and CEO Investment Bank  ⁶Ulrich Körner Group Chief Operating Officer, CEO Corporate Center and CEO UBS Group Europe, Middle East and Africa  ⁷Philip J.  Lofts Group Chief Risk Officer  ⁸Robert J.McCann CEO Wealth Management Americas and CEO UBS Group Americas  ⁹Tom Naratil Group Chief Financial Officer  ¹⁰Alexander Wilmot-Sitwell Co-Chairman and co-CEO of UBS Group Asia Pacific  ¹¹Chi-Won Yoon Co-Chairman and co-CEO of UBS Group Asia Pacific  ¹²Jürg Zeltner CEO UBS Wealth Management and co-CEO Wealth Management & Swiss Bank

Annual Report 2011

The making of UBS

In 2012, UBS celebrates its 150th anniversary. This important milestone in our long history serves to demonstrate the firm’s established and pivotal role in the development and growth of Swiss banking traditions.

Annual Report 2011

Celebrating our 150th anniversary

Operating environment and strategy

Current market climate and industry drivers

Current market climate and industry drivers

Operating environment and strategy

Current market climate and industry drivers

Regulatory developments

In 2011, designing policy measures to address the “too-big-to-fail” issue was the key regulatory focus. Switzerland’s parliament adopted a law to define the regulatory framework for the country’s largest banks, while the G20 heads of states endorsed a set of measures for global systemically important banks, including additional loss absorbency requirements, standards on effective resolution regimes and stricter supervision.

Operating environment and strategy

Regulatory developments

Operating environment and strategy

Our strategy

Our strategy

UBS is a client-focused financial services firm that aims to provide superior financial advice and solutions to clients. Our strategy is shaped by our commitment to deliver attractive and sustainable risk-adjusted returns and takes into account the changing business environment and more stringent capital regulatory requirements. We believe the successful execution of this strategy will enable us to implement a progressive capital returns policy starting with the dividend of CHF 0.10 per share we propose to pay to our shareholders for the financial year 2011.

Annual Report 2012

Our Board of Directors

¹Axel A. Weber Chairman of the Board of Directors, Chairperson of the Governance and Nominating Committee and member of the Corporate Responsibility Committee  ²Isabelle Romy Member of the Audit Committee and the Governance and Nominating Committee  ³David Sidwell Senior Independent Director, Chairperson of the Risk Committee and member of the Governance and Nominating Committee  ⁴Beatrice Weder di Mauro Member of the Audit Committee and Corporate Responsibility Committee  ⁵William G. Parrett Chairperson of the Audit Committee and member of the Corporate Responsibility Committee  ⁶Wolfgang Mayrhuber Chairperson of the Corporate Responsibility Committee and member of the Human Resources and Compensation Committee  ⁷Michel Demaré Independent Vice Chairman, member of the Audit Committee and the Governance and Nominating Committee  ⁸Axel P. Lehmann Member of the Governance and Nominating Committee and the Risk Committee  ⁹Ann F. Godbehere Chairperson of the Human Resources and Compensation Committee and member of the Audit Committee   ¹⁰Rainer-Marc Frey Member of the Human Resources and Compensation Committee and the Risk Committee   ¹¹Joseph Yam Member of the Corporate Responsibility Committee and the Risk Committee  ¹²Helmut Panke Member of the Human Resources and Compensation Committee and the Risk Committee

Annual Report 2012

Our Group Executive Board

¹Sergio P. Ermotti Group CEO  ²Lukas Gähwiler CEO UBS Switzerland and CEO Retail & Corporate  ³Ulrich Körner Group Chief Operating Officer and CEO UBS Group Europe, Middle East and Africa  ⁴Philip J. Lofts Group Chief Risk Officer  ⁵Robert J. McCann CEO Wealth Management Americas and CEO UBS Group Americas  ⁶Jürg Zeltner CEO UBS Wealth Management  ⁷Tom  Naratil Group CFO  ⁸Chi-Won Yoon CEO UBS Group Asia Pacific  ⁹Andrea Orcel CEO Investment Bank  ¹⁰John A. Fraser Chairman and CEO Global Asset Management  ¹¹Markus U. Diethelm Group General Counsel

Annual Report 2012

The making of UBS

UBS has played a pivotal role in the development and growth of Switzerland’s banking tradition since the firm’s origins in the mid-19th century. In 2012, the year of our 150th anniversary, we accelerated our strategic transformation of the firm to create a business model that is better adapted to the new regulatory and market circumstances and that we believe will result in more consistent and high-quality returns.

Annual Report 2012

Our 150th anniversary: an occasion to build and deepen relationships

Operating environment and strategy

Current market climate and industry drivers

Current market climate and industry drivers

Global stock markets rebounded strongly in 2012, supported by confidence-boosting measures in Europe and expansive monetary policy. However, the macroeconomic environment worsened, especially in Europe, as the sovereign debt crisis spilled over to eurozone core countries in the second half of the year. The resulting eurozone recession weakened global economic activity.

Operating environment and strategy

Current market climate and industry drivers

Regulatory developments

In 2012, many regulatory initiatives, launched following the 2007–2009 financial crisis, progressed toward implementation. In particular, changes to capital adequacy and banking ordinances to implement the “too-big-to-fail” law and Basel III in Switzerland were finalized and entered into force on 1 January 2013.

Operating environment and strategy

Regulatory developments