UBS AG — Capital/Financing Update 2011

Dec 20, 2011

Filed Pursuant to Rule 424(b)(2) Registration Statement No. 333-156695

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities Offered	Maximum Aggregate Offering Price	Amount of Registration Fee (1)
Trigger Autocallable Optimization Securities linked to the SPDR ® S&P 500 ® ETF Trust due December 22, 2016	$ 8,896,500.00	$ 1,019.54

(1) Calculated in accordance with Rule 457(r) of the Securities Act of 1933.

PRICING SUPPLEMENT (To Prospectus dated January 13, 2009 and Product Supplement dated January 25, 2011)

UBS AG Trigger Autocallable Optimization Securities

UBS AG $8,896,500 Securities linked to the SPDR ® S&P 500 ® ETF Trust due December 22, 2016

Investment Description

UBS AG Trigger Autocallable Optimization Securities (the “Securities”) are unsubordinated, unsecured debt securities issued by UBS AG (“UBS” or the “Issuer”) linked to the shares of the SPDR ® S&P 500 ® ETF Trust (the “underlying equity”). The Securities are designed for investors who believe that the price of the underlying equity will remain flat or increase during the term of the Securities. If the underlying equity closes at or above the initial price on any observation date (quarterly, beginning after one year), UBS will automatically call the Securities and pay you a call price equal to the principal amount per Security plus a call return. The call return increases the longer the Securities are outstanding. If by maturity the Securities have not been called, UBS will either repay the full principal amount or, if the underlying equity closes below the trigger price on the final valuation date, UBS will repay less than the principal amount, if anything, resulting in a loss on your initial investment that is proportionate to the decline in the price of the underlying equity from the trade date to the final valuation date. Investing in the Securities involves significant risks. The Securities do not pay interest. You may lose some or all of your principal amount. The contingent repayment of principal only applies if you hold the Securities to maturity. Any payment on the Securities, including any repayment of principal, is subject to the creditworthiness of the Issuer. If UBS were to default on its payment obligations you may not receive any amounts owed to you under the Securities and you could lose your entire investment.

Features

q Call Return — UBS will automatically call the Securities for a call price equal to the principal amount plus a call return if the closing price of the underlying equity on any observation date (quarterly, beginning after one year) is equal to or greater than the initial price. The call return increases the longer the Securities are outstanding. If the Securities are not called, investors will have the potential for downside equity market risk at maturity.

q Contingent Repayment of Principal Amount at Maturity — If by maturity the Securities have not been called and the price of the underlying equity does not close below the trigger price on the final valuation date, UBS will pay you the principal amount per Security at maturity. If the price of the underlying equity closes below the trigger price on the final valuation date, UBS will repay less than the principal amount, if anything, resulting in a loss on your initial investment that is proportionate to the decline in the price of the underlying equity from the trade date to the final valuation date. The contingent repayment of principal only applies if you hold the Securities until maturity. Any payment on the Securities, including any repayment of principal, is subject to the creditworthiness of UBS.

Key Dates

Trade Date	December 16, 2011
Settlement Date	December 21, 2011
Observation Dates*	Quarterly, after 1 year (see page 4)
Final Valuation Date*	December 16, 2016
Maturity Date*	December 22, 2016

• Subject to postponement in the event of a market disruption event, as described in the TAOS product supplement.

NOTICE TO INVESTORS: THE SECURITIES ARE SIGNIFICANTLY RISKIER THAN CONVENTIONAL DEBT INSTRUMENTS. THE ISSUER IS NOT NECESSARILY OBLIGATED TO REPAY THE FULL PRINCIPAL AMOUNT OF THE SECURITIES AT MATURITY, AND THE SECURITIES CAN HAVE DOWNSIDE MARKET RISK SIMILAR TO THE UNDERLYING EQUITY. THIS MARKET RISK IS IN ADDITION TO THE CREDIT RISK INHERENT IN PURCHASING A DEBT OBLIGATION OF UBS. YOU SHOULD NOT PURCHASE THE SECURITIES IF YOU DO NOT UNDERSTAND OR ARE NOT COMFORTABLE WITH THE SIGNIFICANT RISKS INVOLVED IN INVESTING IN THE SECURITIES.

YOU SHOULD CAREFULLY CONSIDER THE RISKS DESCRIBED UNDER “KEY RISKS” BEGINNING ON PAGE 5 AND UNDER “RISK FACTORS” BEGINNING ON PAGE PS-13 OF THE TRIGGER AUTOCALLABLE OPTIMIZATION SECURITIES PRODUCT SUPPLEMENT BEFORE PURCHASING ANY SECURITIES. EVENTS RELATING TO ANY OF THOSE RISKS, OR OTHER RISKS AND UNCERTAINTIES, COULD ADVERSELY EFFECT THE MARKET VALUE OF, AND THE RETURN ON, YOUR SECURITIES. YOU MAY LOSE SOME OR ALL OF YOUR INITIAL INVESTMENT IN THE SECURITIES.

Security Offerings

These terms relate to the Securities linked to the shares of the SPDR ® S&P 500 ® ETF Trust. The Securities are offered at a minimum investment of 100 Securities at $10.00 per Security (representing a $1,000 investment) and integral multiples of $10.00 in excess thereof.

Underlying Equity — SPDR ® S&P 500 ® ETF Trust	SPY	Call Return Rate — 10.72% per annum*	Initial Price — $ 121.57	Trigger Price — $ 72.94, which is 60% of the Initial Price	90267U516	US90267U5166

• If the Securities are called, your call return will vary depending on the observation date on which the Securities are called.

See “Additional Information about UBS and the Securities” on page 2. The Securities will have the terms set forth in the Trigger Autocallable Optimization Securities (“TAOS”) product supplement relating to the Securities, dated January 25, 2011, the accompanying prospectus and this pricing supplement.

Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of these Securities or passed upon the adequacy or accuracy of this pricing supplement, or the accompanying product supplement or prospectus. Any representation to the contrary is a criminal offense. The Securities are not deposit liabilities of UBS and are not FDIC insured.

Offering of Securities	Issue Price to Public — Total	Per Security	Underwriting Discount — Total	Per Security	Proceeds to UBS — Total	Per Security
Securities linked to the SPDR ® S&P 500 ® ETF Trust	$8,896,500.00	$10.00	$222,412.50	$0.25	$8,674,087.50	$9.75

UBS Financial Services Inc. Pricing Supplement dated December 16, 2011 UBS Investment Bank

Additional Information about UBS and the Securities

UBS has filed a registration statement (including a prospectus, as supplemented by a product supplement for the securities we may offer, including the Securities) with the Securities and Exchange Commission, or SEC, for the offerings to which this pricing supplement relates. Before you invest, you should read these documents and any other documents relating to the Securities that UBS has filed with the SEC for more complete information about UBS and these offerings. You may obtain these documents for free from the SEC website at www.sec.gov. Our Central Index Key, or CIK, on the SEC website is 0001114446. Alternatively, UBS will arrange to send you these documents if you so request by calling toll-free 800-722-7370.

You may access these documents on the SEC website at www.sec.gov as follows:

¨ TAOS product supplement dated January 25, 2011:

http://www.sec.gov/Archives/edgar/data/1114446/000139340111000037/c207666_690583-424b2.htm

¨ Prospectus dated January 13, 2009:

http://www.sec.gov/Archives/edgar/data/1114446/000095012309000556/y73628b2e424b2.htm

References to “UBS,” “we,” “our” and “us” refer only to UBS AG and not to its consolidated subsidiaries. In this document, “Trigger Autocallable Optimization Securities” or the “Securities” refer to the Securities that are offered hereby. Also, references to the “TAOS product supplement” mean the UBS product supplement, dated January 25, 2011, and references to “accompanying prospectus” mean the UBS prospectus titled, “Debt Securities and Warrants”, dated January 13, 2009.

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Investor Suitability

The Securities may be suitable for you if:

¨ You fully understand the risks inherent in an investment in the Securities, including the risk of loss of your entire initial investment.

¨ You can tolerate a loss of all or a substantial portion of your investment and are willing to make an investment that may have the same downside market risk as an investment in the underlying equity.

¨ You believe the underlying equity will close at or above the initial price on one of the specified observation dates.

¨ You understand and accept that you will not participate in any appreciation in the price of the underlying equity and that your potential return is limited to the applicable call return.

¨ You can tolerate fluctuations in the price of the Securities prior to maturity that may be similar to or exceed the downside price fluctuations of the underlying equity.

¨ You are willing to invest in the Securities based on the call return rate indicated on the cover hereof.

¨ You do not seek current income from this investment and are willing to forgo dividends paid on the underlying equity.

¨ You are willing to invest in securities that may be called early and you are otherwise willing to hold such securities to maturity, a term of approximately 5 years, and accept that there may be little or no secondary market for the Securities.

¨ You are willing to assume the credit risk of UBS for all payments under the Securities, and understand that if UBS defaults on its obligations you may not receive any amounts due to you, including any repayment of principal.

The Securities may not be suitable for you if:

¨ You do not fully understand the risks inherent in an investment in the Securities, including the risk of loss of your entire initial investment.

¨ You cannot tolerate a loss of all or a substantial portion of your investment and are unwilling to make an investment that may have the same downside market risk as an investment in the underlying equity.

¨ You require an investment designed to provide a full return of principal at maturity.

¨ You believe that the price of the underlying equity will decline during the term of the Securities and is likely to close below the trigger price on the final valuation date.

¨ You seek an investment that participates in the full appreciation in the price of the underlying equity or that has unlimited return potential.

¨ You cannot tolerate fluctuations in the price of the Securities prior to maturity that may be similar to or exceed the downside price fluctuations of the underlying equity.

¨ You are unwilling to invest in the Securities based on the call return rate indicated on the cover hereof.

¨ You seek current income from this investment or prefer to receive the dividends paid on the underlying equity.

¨ You are unable or unwilling to hold securities that may be called early, or you are otherwise unable or unwilling to hold such securities to maturity, a term of approximately 5 years, or you seek an investment for which there will be an active secondary market.

¨ You are not willing to assume the credit risk of UBS for all payments under the Securities, including any repayment of principal.

The suitability considerations identified above are not exhaustive. Whether or not the Securities are a suitable investment for you will depend on your individual circumstances and you should reach an investment decision only after you and your investment, legal, tax, accounting and other advisors have carefully considered the suitability of an investment in the Securities in light of your particular circumstances. You should also review carefully the “ Key Risks” beginning on page 5 of this pricing supplement for risks related to an investment in the Securities.

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Final Terms

Issuer	UBS AG, London Branch
Principal Amount	$10.00 per Security (subject to a minimum investment of 100 Securities)
Term (1)	Approximately 5 years, unless called earlier.
Underlying Equity	The shares of the SPDR ® S&P 500 ® ETF Trust.
Call Feature	The Securities will be called if the closing price of the underlying equity on any observation date (quarterly, beginning after one year) is equal to
or greater than the initial price. If the Securities are called, UBS will pay you on the applicable call settlement date a cash payment per Security equal to the call price for the applicable observation date.
Call Settlement Dates	Two business days following each observation date, except that the call settlement date for the final valuation date is the maturity
date.
Call Return	The call return increases the longer the Securities are outstanding and is based upon a rate of 10.72% per annum for the Securities.
Call Price	The call price equals the principal amount per Security plus the applicable call return.

The table below reflects a call return rate of 10.72% per annum for the Securities. Amounts below may have been rounded for ease of reference.

Observation Date (1)	Call Settlement Date		Call Price (per Security)
December 26, 2012	December 28, 2012	10.7200%	$ 11.0720
March 18, 2013	March 20, 2013	13.4000%	$ 11.3400
June 17, 2013	June 19, 2013	16.0800%	$ 11.6080
September 16, 2013	September 18, 2013	18.7600%	$ 11.8760
December 16, 2013	December 18, 2013	21.4400%	$ 12.1440
March 17, 2014	March 19, 2014	24.1200%	$ 12.4120
June 16, 2014	June 18, 2014	26.8000%	$ 12.6800
September 16, 2014	September 18, 2014	29.4800%	$ 12.9480
December 16, 2014	December 18, 2014	32.1600%	$ 13.2160
March 16, 2015	March 18, 2015	34.8400%	$ 13.4840
June 16, 2015	June 18, 2015	37.5200%	$ 13.7520
September 16, 2015	September 18, 2015	40.2000%	$ 14.0200
December 16, 2015	December 18, 2015	42.8800%	$ 14.2880
March 16, 2016	March 18, 2016	45.5600%	$ 14.5560
June 16, 2016	June 20, 2016	48.2400%	$ 14.8240
September 16, 2016	September 20, 2016	50.9200%	$ 15.0920
December 16, 2016	December 22, 2016	53.6000%	$ 15.3600

| Payment at Maturity (per Security) | If the Securities have not been called and the final price is equal to or greater than the trigger
price , at maturity we will pay you an amount in cash equal to the principal amount: $10.00. If the Securities have not been called and the final
price is less than the trigger price , at maturity we will pay you an amount in cash that is less than the principal amount, if anything, resulting in a loss that is proportionate to the decline of the underlying equity, for an amount equal
to: $10.00 + ($10.00 × underlying return). |
| --- | --- |
| Underlying Return | Final Price – Initial Price |
| | Initial Price |
| Trigger Price | $72.94, which is 60% of the initial price (as may be adjusted in the case of certain adjustment events as described under “General Terms of the
Securities — Antidilution Adjustments” in the TAOS product supplement). |
| Initial Price | $121.57, which is the closing price of the underlying equity on the trade date (as may be adjusted in the case of certain adjustment events as
described under “General Terms of the Securities — Antidilution Adjustments” in the TAOS product supplement). |
| Final Price | The closing price of the underlying equity on the final valuation date. |

Investment Timeline

INVESTING IN THE SECURITIES INVOLVES SIGNIFICANT RISKS. YOU MAY LOSE SOME OR ALL OF YOUR PRINCIPAL AMOUNT. ANY PAYMENT ON THE SECURITIES, INCLUDING ANY REPAYMENT OF PRINCIPAL, IS SUBJECT TO THE CREDITWORTHINESS OF UBS. IF UBS WERE TO DEFAULT ON ITS PAYMENT OBLIGATIONS, YOU MAY NOT RECEIVE ANY AMOUNTS OWED TO YOU UNDER THE SECURITIES AND YOU COULD LOSE YOUR ENTIRE INVESTMENT.

(1) Subject to the market disruption event provisions set forth in the TAOS product supplement beginning on page PS-29.

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Key Risks

An investment in any offering of the Securities involves significant risks. Investing in the Securities is not equivalent to investing in the underlying equity. These risks are explained in more detail in the “Risk Factors” section of the TAOS product supplement. We also urge you to consult your investment, legal, tax, accounting and other advisors before you invest in the Securities.

¨ Risk of loss at maturity — The Securities differ from ordinary debt securities in that the issuer will not necessarily pay the full principal amount of the Securities. If the Securities are not called, UBS will repay you the principal amount of your Securities in cash only if the final price of the underlying equity is greater than or equal to the trigger price and will only make such payment at maturity. If the Securities are not called and the final price is less than the trigger price, you will lose some or all of your initial investment in an amount proportionate to the decline in the price of the underlying equity.

¨ The contingent repayment of principal applies only at maturity — You should be willing to hold your Securities to maturity. If you are able to sell your Securities prior to maturity in the secondary market, you may have to sell them at a loss relative to your initial investment even if the price of the underlying equity is above the trigger price.

¨ Your potential return on the Securities is limited to the call return — The return potential of the Securities is limited to the call return regardless of the appreciation of the underlying equity. In addition, because the call return increases the longer the Securities have been outstanding, the call price payable on earlier observation dates is less than the call price payable on later observation dates. The earlier a Security is called, the lower your return will be. If the Securities are not called, you will not participate in any appreciation in the price of the underlying equity even though you will be subject to the risk of a decline in the price of the underlying equity.

¨ Higher call return rates are generally associated with a greater risk of loss — Greater expected volatility with respect to the underlying equity reflects a higher expectation as of the trade date that the price of such equity could close below its trigger price on the final valuation date of the Securities. This greater expected risk will generally be reflected in a higher call return rate for that Security. However, while the call return rate is set on the trade date, an equity’s volatility can change significantly over the term of the Securities. The price of the underlying equity for your Securities could fall sharply, which could result in a significant loss of principal.

¨ No interest payments — UBS will not pay any interest with respect to the Securities.

¨ Reinvestment risk — If your Securities are called early, the term of the Securities will be reduced and you will not receive any payment on the Securities after the applicable call settlement date. There is no guarantee that you would be able to reinvest the proceeds from an automatic call of the Securities at a comparable rate of return for a similar level of risk. To the extent you are able to reinvest such proceeds in an investment comparable to the Securities, you may incur transaction costs such as dealer discounts and hedging costs built into the price of the new securities. Because the Securities may be called as early as 1 year after issuance, you should be prepared in the event the Securities are called early.

¨ Credit risk of UBS — The Securities are unsubordinated, unsecured debt obligations of the Issuer, UBS, and are not, either directly or indirectly, an obligation of any third party. Any payment to be made on the Securities, including payments in respect of an automatic call or any repayment of principal, depends on the ability of UBS to satisfy its obligations as they come due. As a result, the actual and perceived creditworthiness of UBS may affect the market value of the Securities and, in the event UBS were to default on its obligations, you may not receive any amounts owed to you under the terms of the Securities and you could lose your entire initial investment.

¨ Market risk — The price of the underlying equity can rise or fall sharply due to factors specific to that underlying equity or the securities constituting the assets of the underlying equity. These factors may include price volatility, earnings, financial conditions, corporate, industry and regulatory developments, management changes and decisions and other events, as well as general market factors, such as general market volatility and levels, interest rates and economic and political conditions. We urge you to review financial and other information filed periodically by the underlying equity with the SEC.

¨ Owning the Securities is not the same as owning the underlying equity — The return on your Securities is unlikely to reflect the return you would realize if you actually owned the underlying equity. For instance, you will not receive or be entitled to receive any dividend payments or other distributions on the underlying equity during the term of your Securities. As an owner of the Securities, you will not have voting rights or any other rights that holders of the underlying equity may have. Furthermore, the underlying equity may appreciate substantially during the term of the Securities and you will not participate in such appreciation.

¨ No assurance that the investment view implicit in the Securities will be successful — It is impossible to predict whether the price of the underlying equity will rise or fall. The closing price of the underlying equity will be influenced by complex and interrelated political, economic, financial and other factors that affect the underlying equity. You should be willing to accept the downside risks of owning equities in general and the underlying equity in particular, and to assume the risk that, if the Securities are not automatically called, you will not receive any positive return on your Securities and you may lose some or all of your initial investment.

¨ The calculation agent can make adjustments that affect the payment to you at maturity — For certain corporate events affecting the underlying equity, the calculation agent may make adjustments to the initial price or trigger price. However, the calculation agent will not make an adjustment in response to all events that could affect the underlying equity. If an event occurs that does not require the calculation agent to make an adjustment, the value of the Securities may be materially and adversely affected. In addition, all determinations and calculations concerning any such adjustments will be made by the calculation agent. You should be aware that the calculation agent may make any such adjustment, determination or calculation in a manner that differs from that discussed in the product supplement as necessary to achieve an equitable result. Following a delisting or discontinuance of the underlying equity, the amount you receive at maturity may be based on a share of another exchange traded fund. The occurrence of these events and the

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consequent adjustments may materially and adversely affect the value of the Securities. For more information, see the section “General Terms of the Securities — Antidilution Adjustments” and “General Terms of the Securities — Delisting, Discontinuance or Modification of an ETF” in the product supplement. Regardless of any of the events discussed above, any payment on the Securities is subject to the creditworthiness of UBS.

¨ The value of the underlying equity may not completely track the value of the securities in which such exchange traded fund invests — Although the trading characteristics and valuations of the underlying equity will usually mirror the characteristics and valuations of the securities in which such exchange traded fund invests, its value may not completely track the value of such securities. The value of the underlying equity will reflect transaction costs and fees that the securities in which that exchange traded fund invests do not have. In addition, although the underlying equity may be currently listed for trading on an exchange, there is no assurance that an active trading market will continue for such underlying equity or that there will be liquidity in the trading market.

¨ Fluctuation of NAV — The net asset value (the “NAV”) of an exchange traded fund may fluctuate with changes in the market value of such exchange traded fund’s securities holdings. The market prices of the underlying equity may fluctuate in accordance with changes in NAV and supply and demand on the applicable stock exchanges. In addition, the market price of the underlying equity may differ from its NAV per share; the underlying equity may trade at, above or below its NAV per share.

¨ Failure of the underlying equity to track the level of the underlying index — While the underlying equity is designed and intended to track the level of a specific index (an ”underlying index”), various factors, including fees and other transaction costs, will prevent the underlying equity from correlating exactly with changes in the level of such underlying index. Accordingly, the performance of the underlying equity will not be equal to the performance of its underlying index during the term of the Securities.

¨ There may be little or no secondary market — The Securities will not be listed or displayed on any securities exchange or any electronic communications network. There can be no assurance that a secondary market for the Securities will develop. UBS Securities LLC and other affiliates of UBS may make a market in the offering of the Securities, although they are not required to do so and may stop making a market at any time. If you are able to sell your Securities prior to maturity, you may have to sell them at a substantial loss.

¨ Price of Securities prior to maturity — The market price of the Securities will be influenced by many unpredictable and interrelated factors, including the price of the underlying equity; the volatility of the underlying equity; the dividend rate paid on the underlying equity; the time remaining to the maturity of the Securities; interest rates in the markets; geopolitical conditions and economic, financial, political and regulatory or judicial events; and the creditworthiness of UBS.

¨ Impact of fees on secondary market prices — Generally, the price of the Securities in the secondary market is likely to be lower than the initial price to public since the initial price to public included, and the secondary market prices are likely to exclude, commissions, hedging costs or other compensation paid with respect to the Securities.

¨ Potential UBS impact on price — Trading or transactions by UBS or its affiliates in the underlying equity and/or over-the-counter options, futures or other instruments with returns linked to the performance of the underlying equity may adversely affect the performance and, therefore, the market value of the Securities.

¨ Potential conflict of interest — UBS and its affiliates may engage in business with the issuer of the underlying equity, which may present a conflict between the obligations of UBS and you, as a holder of the Securities. There are also potential conflicts of interest between you and the calculation agent, which will be an affiliate of UBS.

¨ Potentially inconsistent research, opinions or recommendations by UBS — UBS and its affiliates publish research from time to time on financial markets and other matters that may influence the value of the Securities, or express opinions or provide recommendations that are inconsistent with purchasing or holding the Securities. Any research, opinions or recommendations expressed by UBS or its affiliates may not be consistent with each other and may be modified from time to time without notice. Investors should make their own independent investigation of the merits of investing in the Securities and the underlying equity to which the Securities are linked.

¨ Dealer incentives — UBS and its affiliates act in various capacities with respect to the Securities. We and our affiliates may act as a principal, agent or dealer in connection with the sale of the Securities. Such affiliates, including the sales representatives, will derive compensation from the distribution of the Securities and such compensation may serve as an incentive to sell these Securities instead of other investments. We will pay total underwriting compensation of $0.25 per Security to any of our affiliates acting as agents or dealers in connection with the distribution of the Securities.

¨ Uncertain tax treatment — Significant aspects of the tax treatment of the Securities are uncertain. You should consult your own tax advisor about your tax situation.

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Hypothetical Examples

The examples below illustrate the payment upon a call or at maturity for a $10.00 Security on a hypothetical offering of the Securities, with the following assumptions (amounts have been rounded for ease of reference):

Principal Amount:	$10.00
Term:	5 years
Initial Price:	$121.57
Call Return Rate:	10.72% per annum (or 2.68% per quarterly period)
Observation Dates:	Quarterly, beginning after 1 year
Trigger Price:	$72.94 (which is 60% of the Initial Price)

Example 1 — Securities are Called on the First Observation Date

Closing Price at first Observation Date:	$130.00 (at or above Initial Price, Securities are called)
Call Price (per Security):	$11.0720

Since the Securities are called on the first observation date (which is approximately one year after the trade date), UBS will pay you on the call settlement date a total call price of $11.0720 per $10.00 principal amount (10.72% return on the Securities).

Example 2 — Securities are Called on the Final Valuation Date

Closing Price at first Observation Date:	$120.00 (below Initial Price, Securities NOT called)
Closing Price at second Observation Date:	$110.00 (below Initial Price, Securities NOT called)
Closing Price at third Observation Date:	$100.00 (below Initial Price, Securities NOT called)
Closing Price at fourth to sixteenth Observation Date:	Various (each below Initial Price, Securities NOT called)
Closing Price at Final Valuation Date:	$130.00 (at or above Initial Price, Securities are called)
Call Price (per Security):	$15.3600

Since the Securities are called on the final valuation date, UBS will pay you on the call settlement date (which coincides with the maturity date in this example) a total call price of $15.3600 per $10.00 principal amount (53.60% return on the Securities).

Example 3 — Securities are NOT Called and the Final Price is above the Trigger Price

Closing Price at first Observation Date:	$120.00 (below Initial Price, Securities NOT called)
Closing Price at second Observation Date:	$110.00 (below Initial Price, Securities NOT called)
Closing Price at third Observation Date:	$100.00 (below Initial Price, Securities NOT called)
Closing Price at fourth to sixteenth Observation Date:	Various (each below Initial Price, Securities NOT called)
Closing Price at Final Valuation Date:	$90.00 (below Initial Price, but above Trigger Price, Securities NOT called)
Settlement Amount (per Security):	$10.00

Since the Securities are not called and the final price is above or equal to the trigger price, at maturity UBS will pay you a total of $10.00 per $10.00 principal amount (a zero percent return on the Securities).

Example 4 — Securities are NOT Called and the Final Price is below the Trigger Price

Closing Price at first Observation Date:	$110.00 (below Initial Price, Securities NOT called)
Closing Price at second Observation Date:	$90.00 (below Initial Price, Securities NOT called)
Closing Price at third Observation Date:	$70.00 (below Initial Price and Trigger Price, Securities NOT called)
Closing Price at fourth to sixteenth Observation Date:	Various (each below Initial Price, Securities NOT called)
Closing Price at Final Valuation Date:	$48.63 (below Initial Price and Trigger Price, Securities NOT called)
Settlement Amount (per Security):	$10.00 + ($10 × Underlying Return)
	$10.00 + ($10 × -60%)
	$10.00 – $6.00
	$4.00

Since the Securities are not called and the final price is below the trigger price, at maturity UBS will pay you a total of $4.00 per $10.00 principal amount (a 60% loss on the Securities).

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Information about the Underlying Equity

All disclosures contained in this pricing supplement regarding the underlying equity are derived from publicly available information. Neither UBS nor any of its affiliates assumes any responsibilities for the adequacy or accuracy of information about the underlying equity contained in this pricing supplement. You should make your own investigation into the underlying equity.

Included on the following pages is a brief description of the underlying equity. This information has been obtained from publicly available sources. Set forth below is a table that provides the quarterly high and low closing prices for the underlying equity. The information given below is for the four calendar quarters in each of 2007, 2008, 2009 and 2010 and the first, second and third calendar quarters of 2011. Partial data is provided for the fourth calendar quarter of 2011. We obtained the closing price information set forth below from the Bloomberg Professional service (“Bloomberg”) without independent verification. You should not take the historical prices of the underlying equity as an indication of future performance.

The underlying equity is registered under the Securities Exchange Act of 1934 (the “Exchange Act”). Companies with securities registered under the Exchange Act are required to file financial and other information specified by the SEC periodically. Information filed by the underlying equity with the SEC can be reviewed electronically through a website maintained by the SEC. The address of the SEC’s website is http://www.sec.gov. Information filed with the SEC by the underlying equity issuer under the Exchange Act can be located by reference to its SEC file number provided below. In addition, information filed with the SEC can be inspected and copied at the Public Reference Section of the SEC, 100 F Street, N.E., Room 1580, Washington, D.C. 20549. Copies of this material can also be obtained from the Public Reference Section, at prescribed rates.

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SPDR ® S&P 500 ® ETF Trust

We have derived all information contained in this pricing supplement regarding the SPDR ® S&P 500 ® ETF Trust (formerly the SPDR Trust, Series I; the “SPY Fund”) from publicly available information. Such information reflects the policies of, and is subject to change by, PDR Services LLC, the sponsor of the SPY Fund and State Street Bank and Trust Company, the trustee of the SPY Fund (the “Trustee”). We make no representations or warranty as to the accuracy or completeness of the information derived from these public sources.

The SPY Fund is a unit investment trust that issues depositary receipts of the SPY Fund (the “SPDRs”), each of which represents a fractional undivided ownership interest in the SPY Fund. The SPY Fund is designed to generally correspond to the price and yield performance, before fees and expenses, of the S&P 500 ® Index. The Trustee on a nondiscretionary basis adjusts the composition of the portfolio of stocks held by the SPY Fund to conform to changes in the composition and/or weighting structure of the S&P 500 ® Index. Although the SPY Fund may at any time fail to own certain securities included within the S&P 500 ® Index, the Trust will be substantially invested in the constituent stocks of the S&P 500 ® Index.

The S&P 500 ® Index was developed by Standard & Poor’s Financial Services LLC, a subsidiary of The McGraw-Hill Companies, Inc. (“S&P”) and is calculated, maintained and published by S&P. S&P is under no obligation to continue to publish, and may discontinue or suspend the publication of the S&P 500 ® Index at any time. The S&P 500 ® Index is composed of five-hundred (500) selected stocks of United States companies, all of which are listed on national stock exchanges and spans over 24 separate industry groups. Since 1968, the S&P 500 ® Index has been a component of the U.S. Commerce Department’s list of Leading Indicators that track key sectors of the U.S. economy.

As of December 16, 2011, ordinary operating expenses of the SPY Fund are expected to accrue at an annual rate of 0.0945% of the SPY Fund’s daily net asset value. Expenses of the SPY Fund reduce the net value of the assets held by the SPY Fund and, therefore, reduce the value of each SPDR.

As of September 30, 2011, the SPY Fund held stocks of U.S. companies in the following industry sectors: information technology (19.44%), financials (13.58%), health care (12.13%), consumer staples (11.68%), energy (11.61%), consumer discretionary (10.65%), industrials (10.27%), utilities (3.95%), materials (3.35%) and telecommunication services (3.29%).

Information filed by the SPDR Trust with the SEC under the Securities Exchange Act and the Investment Company Act can be found by reference to its SEC file number: 001-11672 and 811-06125. The SPY Fund’s website is https://www.spdrs.com/product/ fund.seam?ticker=spy. The SPDR’s are listed on the NYSE Arca under ticker symbol “SPY.” Information from outside sources is not incorporated by reference in, and should not be considered part of, this pricing supplement or any accompanying prospectus. We make no representation or warranty as to the accuracy or completeness of the information contained in outside sources.

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Historical Information

The following table sets forth the quarterly high and low closing prices for the SPY Fund, based on daily closing prices as reported by Bloomberg. The closing price of the SPY Fund on December 16, 2011 was $121.57. Past performance of the SPY Fund is not indicative of the future performance of the SPY Fund.

Quarter Begin	Quarter End	Quarterly High	Quarterly Low	Quarterly Close
1/3/2007	3/30/2007	$146.01	$137.41	$142.07
4/2/2007	6/29/2007	$154.15	$142.24	$150.38
7/2/2007	9/28/2007	$155.03	$141.13	$152.67
10/1/2007	12/31/2007	$156.44	$140.90	$146.39
1/2/2008	3/31/2008	$144.94	$127.90	$131.89
4/1/2008	6/30/2008	$143.08	$127.69	$128.04
7/1/2008	9/30/2008	$130.70	$111.38	$116.54
10/1/2008	12/31/2008	$116.00	$75.95	$ 90.33
1/2/2009	3/31/2009	$ 93.44	$68.11	$ 79.44
4/1/2009	6/30/2009	$ 95.09	$81.00	$ 91.92
7/1/2009	9/30/2009	$107.33	$87.95	$105.56
10/1/2009	12/31/2009	$112.67	$102.54	$111.44
1/4/2010	3/31/2010	$117.40	$105.87	$116.99
4/1/2010	6/30/2010	$121.79	$103.22	$103.22
7/1/2010	9/30/2010	$114.79	$102.20	$114.12
10/1/2010	12/31/2010	$125.92	$113.75	$125.78
1/3/2011	3/31/2011	$134.57	$126.21	$132.51
4/1/2011	6/30/2011	$136.54	$126.81	$131.97
7/1/2011	9/30/2011	$135.46	$112.26	$113.17
10/3/2011*	12/16/2011*	$128.68	$109.93	$121.57

• As of the date of this pricing supplement, available information for the fourth calendar quarter of 2011 includes data for the period from October 3, 2011 through December 16, 2011. Accordingly, the “Quarterly High,” “Quarterly Low” and “Quarterly Close” data indicated are for this shortened period only and do not reflect complete data for the fourth calendar quarter of 2011.

The graph below illustrates the performance of the SPY Fund from January 3, 2000 through December 16, 2011, based on information from Bloomberg. The dotted line represents the trigger price of $72.94, which is equal to 60% of the closing price on December 16, 2011. Past performance of the SPY Fund is not indicative of the future performance of the SPY Fund.

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What are the Tax Consequences of the Securities?

The United States federal income tax consequences of your investment in the Securities are uncertain. Some of these tax consequences are summarized below, but we urge you to read the more detailed discussion in “Supplemental U.S. Tax Considerations” beginning on page PS-43 of the TAOS product supplement and to discuss the tax consequences of your particular situation with your tax advisor.

Pursuant to the terms of the Securities, UBS and you agree, in the absence of a statutory, regulatory, administrative or judicial ruling to the contrary, to characterize the Securities as a pre-paid derivative contract with respect to the underlying equity. If your Securities are so treated, you should generally recognize capital gain or loss upon the sale, automatic call, redemption or maturity of your Securities in an amount equal to the difference between the amount you receive at such time and the amount you paid for your Securities. Such gain or loss should generally be long term capital gain or loss if you have held your Securities for more than one year.

Unless otherwise specified in this applicable pricing supplement, in the opinion of our counsel, Cadwalader, Wickersham & Taft LLP, it would be reasonable to treat your Securities in the manner described above. However, because there is no authority that specifically addresses the tax treatment of the Securities, it is possible that your Securities could alternatively be treated for tax purposes in the manner described under “Supplemental U.S. Tax Considerations — Alternative Treatments” beginning on page PS-45 of the TAOS product supplement including possible treatment as a ‘constructive ownership transaction’ subject to the constructive ownership rules of Section 1260 of the Code, as described in such product supplement. The risk that the Securities may be recharacterized for United States federal income tax purposes as instruments giving rise to current ordinary income (even before receipt of any cash) and short-term capital gain or loss (even if held for more than one year), is higher than with other equity-linked securities that similarly do not guarantee full repayment of principal.

In 2007, the Internal Revenue Service released a notice that may affect the taxation of holders of the Securities. According to the notice, the Internal Revenue Service and the Treasury Department are actively considering whether the holder of an instrument such as the Securities should be required to accrue ordinary income on a current basis. It is not possible to determine what guidance they will ultimately issue, if any. It is possible, however, that under such guidance, holders of the Securities will ultimately be required to accrue income currently and this could be applied on a retroactive basis. The Internal Revenue Service and the Treasury Department are also considering other relevant issues, including whether additional gain or loss from such instruments should be treated as ordinary or capital, whether foreign holders of such instruments should be subject to withholding tax on any deemed income accruals, and whether the special “constructive ownership rules” of Section 1260 of the Internal Revenue Code should be applied to such instruments. Holders are urged to consult their tax advisors concerning the significance, and the potential impact, of the above considerations. Except to the extent otherwise required by law, UBS intends to treat your Securities for United States federal income tax purposes in accordance with the treatment described above and under “Supplemental U.S. Tax Considerations” beginning on page PS-43 of the TAOS product supplement unless and until such time as the Treasury Department and Internal Revenue Service determine that some other treatment is more appropriate.

Beginning in 2013, U.S. holders that are individuals, estates, and certain trusts will be subject to an additional 3.8% tax on all or a portion of their “net investment income,” which may include any gain realized with respect to the Securities, to the extent of their net investment income that when added to their other modified adjusted gross income, exceeds $200,000 for an unmarried individual, $250,000 for a married taxpayer filing a joint return (or a surviving spouse), or $125,000 for a married individual filing a separate return. U.S. holders should consult their tax advisors with respect to their consequences with respect to the 3.8% Medicare tax.

Moreover, in 2007, legislation was introduced in Congress that, if enacted, would have required holders of Securities purchased after the bill was enacted to accrue interest income over the term of the Securities despite the fact that there will be no interest payments over the term of the Securities. It is not possible to predict whether a similar or identical bill will be enacted in the future, or whether any such bill would affect the tax treatment of your Securities.

Specified Foreign Financial Assets . Under recently enacted legislation, individuals that own “specified foreign financial assets” may be required to file information with respect to such assets with their tax returns, especially if such assets are held outside the custody of a U.S. financial institution. You are urged to consult your tax advisor as to the application of this legislation to your ownership of the Securities.

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Supplemental Plan of Distribution (Conflicts of Interest)

We have agreed to sell to UBS Financial Services Inc. and certain of its affiliates, together the “Agents,” and the Agents have agreed to purchase, all of the Securities at the issue price less the underwriting discount indicated on the cover of this pricing supplement, the document filed pursuant to Rule 424(b) containing the final pricing terms of the Securities.

We or one of our affiliates may enter into swap agreements or related hedge transactions with one of our other affiliates or unaffiliated counterparties in connection with the sale of the Securities and UBS or its affiliates may earn additional income as a result of payments pursuant to the swap or related hedge transactions.

Conflicts of Interest — Each of UBS Securities LLC and UBS Financial Services Inc. is an affiliate of UBS and, as such, has a “conflict of interest” in this offering within the meaning of FINRA Rule 5121. In addition, UBS will receive the net proceeds (excluding the underwriting discount) from the initial public offering of the Securities, thus creating an additional conflict of interest within the meaning of Rule 5121. Consequently, the offering is being conducted in compliance with the provisions of Rule 5121. Neither UBS Securities LLC nor UBS Financial Services Inc. is permitted to sell Securities in this offering to an account over which it exercises discretionary authority without the prior specific written approval of the account holder.

Structured Product Categorization

To help investors identify appropriate Structured Products (“Structured Products”), UBS organizes its Structured Products into four categories: Protection Strategies, Optimization Strategies, Performance Strategies and Leverage Strategies. The Securities are classified by UBS as an Optimization Strategy for this purpose. The description below is intended to describe generally the four categories of Structured Products and the types of principal repayment features that may be offered on those products. This description should not be relied upon as a description of any particular Structured Product.

¨ Protection Strategies are structured to complement and provide the potential to outperform traditional fixed income instruments. These Structured Products are generally designed for investors with low to moderate risk tolerances.

¨ Optimization Strategies provide the opportunity to enhance market returns or yields and can be structured with full downside market exposure or with buffered or contingent downside market exposure. These structured products are generally designed for investors who can tolerate downside market risk.

¨ Performance Strategies provide efficient access to markets and can be structured with full downside market exposure or with buffered or contingent downside market exposure. These structured products are generally designed for investors who can tolerate downside market risk.

¨ Leverage Strategies provide leveraged exposure to the performance of an underlying asset. These Structured Products are generally designed for investors with high risk tolerances.

In order to benefit from any type of principal repayment feature, investors must hold the Securities to maturity.

Classification of Structured Products into categories is for informational purposes only and is not intended to guarantee particular results or performance.

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