UBS AG — Regulatory Filings 2012

May 1, 2012

Filed Pursuant to Rule 424(b)(2) Registration Statement No. 333-178960

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities Offered		Amount of Registration Fee (1)
Trigger PLUS Based on the Value of the EURO STOXX 50 ® Index due July 27, 2015	$5,250,000.00	$601.65

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

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April 2012 PRICING SUPPLEMENT (To Prospectus date January 11, 2012 and Product Supplement dated April 26, 2012)

STRUCTURED INVESTMENTS

Opportunities in International Equities

$5,250,000 Trigger Performance Leverage Upside Securities Based on the Value of the EURO STOXX 50 ® Index due July 27, 2015

Trigger Performance Leverage Upside Securities

The Trigger Performance Leverage Upside Securities (the “Trigger PLUS”) offer leveraged exposure to the EURO STOXX 50 ® Index (the “underlying index”), while providing contingent repayment of principal in the case of negative performance by the underlying index so long as the final index value is equal to or above a certain level (the “trigger value”). In exchange for enhanced positive index performance investors are exposed to the risk of loss of some or all of their investment if the final index value is below the trigger value. At maturity, if the value of the underlying index has decreased below the trigger value, the investor is fully exposed to the negative index performance. At maturity, if the underlying index has appreciated, investors will receive the stated principal amount of their investment plus the leveraged upside performance of the underlying index. Accordingly, the Trigger PLUS do not guarantee any return of principal at maturity. The Trigger PLUS are unsubordinated, unsecured debt obligations issued by UBS AG (“UBS”), and all payments on the Trigger PLUS are subject to the credit risk of UBS. If UBS were to default on its payment obligations you may not receive any amounts owed to you under the Trigger PLUS and you could lose your entire investment.

SUMMARY TERMS
Issuer:	UBS AG, London Branch
Underlying index:	EURO STOXX 50 ® Index
Aggregate principal amount:	$5,250,000
Stated principal amount:	$10 per security
Issue price:	$10 per security (see “Commissions and issue price” below)
Pricing date:	April 27, 2012
Original issue date:	May 2, 2012
Maturity date:	July 27, 2015, subject to postponement in the
event of a market disruption event, as described in the accompanying product supplement
Payment at maturity:	§ If
the final index value is greater than the initial index value: $10 + leveraged upside payment. § If
the final index value is less than or equal to the initial index value but equal to or greater than the trigger value: $10 § If
the final index value is less than the trigger value: $10 + ($10 x index performance factor) This amount will be less than the stated principal amount of $10 and could be zero. There is no minimum payment at maturity
on the Trigger PLUS. Investors may lose their entire investment.
Index performance factor:	(final index value - initial index value) / initial index value
Leveraged upside payment:	$10 x leverage factor x index performance factor
Initial index value:	2,344.02, which is the closing value of the underlying index on the
pricing date
Final index value:	The closing value of the underlying index on the valuation date
Valuation date:	July 22, 2015, subject to postponement in the event of a market
disruption event, as described in the accompanying product supplement
Leverage factor:	2
Trigger value:	1,758.02, which is 75% of the initial index value
CUSIP:	9026M0812
ISIN:	US9026M08126
Listing:	The Trigger PLUS will not be listed on any securities exchange.
Agent:	UBS Securities LLC

| Commissions
and issue price: | Price
to public | Fees and Commissions (1) | Proceeds to issuer |
| --- | --- | --- | --- |
| Per security | $10.00 | $0.30 | $9.70 |
| Total | $5,250,000 | $157,500 | $5,092,500 |

(1) UBS Securities LLC, acting as agent for UBS, will receive a fee of $0.30 per $10.00 stated principal amount of Trigger PLUS and will pay the entire fee to Morgan Stanley Smith Barney LLC as a fixed sales commission of $0.30 per $10.00 stated principal amount of Trigger PLUS that Morgan Stanley Smith Barney LLC sells. See “Supplemental Information Concerning Plan of Distribution; Conflicts of Interest”.

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

YOU SHOULD CAREFULLY CONSIDER THE RISKS DESCRIBED UNDER ‘‘RISK FACTORS’’ BEGINNING ON PAGE 12 AND UNDER ‘‘RISK FACTORS’’ BEGINNING ON PAGE PS-14 OF THE PRODUCT SUPPLEMENT BEFORE PURCHASING ANY TRIGGER PLUS. EVENTS RELATING TO ANY OF THOSE RISKS, OR OTHER RISKS AND UNCERTAINTIES, COULD ADVERSELY AFFECT THE MARKET VALUE OF, AND THE RETURN ON, YOUR TRIGGER PLUS. YOU MAY LOSE SOME OR ALL OF YOUR INITIAL INVESTMENT IN THE TRIGGER PLUS.

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

THE TRIGGER PLUS ARE NOT BANK DEPOSITS AND ARE NOT INSURED OR GUARANTEED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENTAL AGENCY, NOR ARE THEY OBLIGATIONS OF, OR GUARANTEED BY, A BANK.

Pricing Supplement dated April 27, 2012

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Trigger PLUS Based on the Value of the EUROSTOXX 50 Index due July 27, 2015

Additional Information about UBS and the Trigger Plus

UBS has filed a registration statement (including a prospectus as supplemented by a product supplement for the Trigger PLUS and an index supplement for various securities we may offer, including the Trigger PLUS) with the Securities and Exchange Commission, or SEC, for the offering to which this document relates. Before you invest, you should read these documents and any other documents relating to this offering that UBS has filed with the SEC for more complete information about UBS and this offering. You may obtain these documents for free from the SEC website at www.sec.gov. Our Central Index Key, or CIK, on the SEC web site is 0001114446. Alternatively, UBS will arrange to send you these documents if you so request by calling toll-free 1-877-387-2275.

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

Product Supplement dated April 26, 2012:

http://www.sec.gov/Archives/edgar/data/1114446/000139340112000047/c310542_690708-424b2.htm

Index Supplement dated January 24, 2012:

http://www.sec.gov/Archives/edgar/data/1114446/000119312512021889/d287369d424b2.htm

Prospectus dated January 11, 2012: http://www.sec.gov/Archives/edgar/data/1114446/000119312512008669/d279364d424b3.htm

References to “UBS,” “we,” “our” and “us” refer only to UBS AG and not to its consolidated subsidiaries. In this document, the “Trigger PLUS” refers to the Trigger Performance Leveraged Upside Securities that are offered hereby. Also, references to the “accompanying prospectus” mean the UBS prospectus titled “Debt Securities and Warrants,” dated January 11, 2012, references to the “index supplement” mean the UBS index supplement, dated January 24, 2012 and references to the “accompanying product supplement” mean the UBS product supplement “Trigger Performance Leveraged Upside Securities”, dated April 26, 2012.

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

UBS reserves the right to change the terms of, or reject any offer to purchase, the Trigger PLUS prior to their issuance. In the event of any changes to the terms of the Trigger PLUS, UBS will notify you and you will be asked to accept such changes in connection with your purchase. You may also choose to reject such changes in which case UBS may reject your offer to purchase.

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Trigger PLUS Based on the Value of the EUROSTOXX 50 Index due July 27, 2015

Investment Overview

Trigger Performance Leveraged Upside Securities

The Trigger PLUS Based on the EURO STOXX 50 ® Index due July 27, 2015 can be used:

§ As an alternative to direct exposure to the underlying index that enhances the return on any positive performance of the underlying index; however, by investing in the Trigger PLUS, you will not be entitled to receive any dividends paid with respect to the stocks that constitute the underlying index. You should carefully consider whether an investment that does not provide for dividends or periodic interest payments is appropriate for you

§ To enhance returns and outperform the underlying index in a bullish scenario

§ To achieve similar levels of upside exposure to the underlying index as a direct investment while using fewer dollars by taking advantage of the leverage factor

§ To provide a return of principal in the event of a decline in the underlying index from the pricing date to the valuation date, but only if the final index value is greater than or equal to the trigger value

Maturity:	Approximately 3 years
Leverage factor:	2
Trigger value:	75% of the initial index value
Coupon:	None

Key Investment Rationale

Investors can use the Trigger PLUS to leverage returns by a factor of 2 and obtain contingent protection against a loss of principal in the event of a decline in the underlying index on the valuation date, but only if the final index value is greater than the trigger value. The trigger value is 75% of the initial index value.

Investors will not be entitled to receive any dividends paid with respect to the stocks that constitute the underlying index. You should carefully consider whether an investment that does not provide for dividends or periodic interest is appropriate for you. The payment scenarios below do not show any effect of lost dividend yield over the term of the Trigger PLUS.

Leveraged Performance	The Trigger PLUS offer investors an opportunity to capture enhanced returns on any positive performance relative to a direct investment in the underlying index.
Trigger Feature	At maturity, even if the underlying index has declined over the term
of the Trigger PLUS, you will receive your stated principal amount but only if the final index value is greater than or
equal to the trigger value.
Upside Scenario	The underlying index increases in value from the pricing date to the valuation date and, at maturity, the Trigger PLUS redeem for the stated principal amount of $10 plus 2 times the index performance factor.
Par Scenario	The final index value is less than or equal to the initial index value but is equal to or greater than the trigger value. In this case, you receive the full stated principal amount at maturity even though the value of the underlying index has depreciated.
Downside Scenario	The underlying index declines in value by more than 25% from the
pricing date to the valuation date. At maturity, the Trigger PLUS redeem for at least 25% less than the stated principal
amount (and could redeem for zero), and this decrease will be by an amount proportionate to the full amount of the
decline in the value of the underlying index from the pricing date to the valuation date. (Example: if the underlying
index decreases in value by 35%, the Trigger PLUS will redeem for $6.50, or 65% of the stated principal amount.)

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Trigger PLUS Based on the Value of the EUROSTOXX 50 Index due July 27, 2015

Investor Suitability

The Trigger PLUS may be suitable for you if:

§ You fully understand the risks inherent in an investment in the Trigger PLUS, 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 index or the index constituents.

§ You believe the final index value of the underlying index is not likely to be less than the trigger value and, if it is, you can tolerate receiving a payment at maturity that will likely be less than your principal amount and may be zero.

§ You can tolerate fluctuations in the price of the Trigger PLUS prior to maturity that may be similar to or exceed the downside price fluctuations of the underlying index.

§ You do not seek current income from your investment and are willing to forego dividends paid on any index constituent stocks.

§ You are willing and able to hold the Trigger PLUS to maturity, a term of approximately 39 months, and accept that there may be little or no secondary market for the Trigger PLUS.

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

The Trigger PLUS may not be suitable for you if:

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

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

§ You are not willing to make an investment that may have the same downside market risk as an investment in the underlying index or the index constituents.

§ You believe the final index value of the underlying index is likely to be less than the trigger value, which could result in a total loss of your initial investment.

§ You cannot tolerate fluctuations in the price of the Trigger PLUS prior to maturity that may be similar to or exceed the downside price fluctuations of the underlying index

§ You seek current income from this investment or prefer to receive the dividends paid on the index constituent stocks.

§ You are unable or unwilling to hold the Trigger PLUS to maturity, a term of approximately 39 months, and 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 Trigger PLUS, including any repayment of principal.

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Fact Sheet

The Trigger PLUS offered are unsubordinated, unsecured debt securities issued by UBS, will pay no interest, do not guarantee any return of principal at maturity and are subject to the terms described in the accompanying product supplement and prospectus, as supplemented or modified by this pricing supplement. At maturity, an investor will receive for each security that the investor holds an amount in cash that may be greater than, equal to or less than the stated principal amount based upon the closing value of the underlying index on the valuation date. The Trigger PLUS do not guarantee any return of principal at maturity. All payments on the Trigger PLUS are subject to the credit risk of UBS. If UBS were to default on its payment obligations you may not receive any amount owed to you under the Trigger PLUS and you could lose your entire investment.

Expected Key Dates — Pricing date:	Original issue date (settlement date):	Valuation date	Maturity date:
April 27, 2012	May 2, 2012 (3 business days after the pricing date)	July 22,
2015	July 27, 2015

Key Terms
Issuer:	UBS AG, London Branch
Underlying index:	EURO STOXX 50 ® Index
Aggregate principal amount:	$5,250,000
Stated principal amount:	$10 per security
Issue price:	$10 per security
Denominations:	$10 per security and integral multiples thereof
Interest:	None
Payment at maturity:	§ If
the final index value is greater than the initial index value: $10 + leveraged upside payment. § If
the final index value is less than or equal to the initial index value but equal to or greater than the trigger value: $10 § If
the final index value is less than the trigger value: $10 + ($10 x index performance factor) This amount will be less than the stated principal amount of $10 and could be zero. There is no minimum payment at maturity
on the Trigger PLUS. Investor may lose their entire investment.
Index performance factor:	(final index value - initial index value) / initial index value
Trigger value:	1,758.02, which is 75% of the initial index value
Leveraged upside payment:	$10 x leverage factor x index performance factor
Initial index value:	2,344.02, which is the closing value of the underlying index on the pricing date
Final index value:	The closing value of the underlying index on the valuation date
Valuation date:	July 22, 2015, subject to postponement for non-underlying asset business days and certain
market disruption events
Risk factors:	Please see “Risk Factors” beginning on page 12.

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General Information
Listing:	The Trigger PLUS will not be listed on any securities exchange.
CUSIP:	· 9026M0812
ISIN:	· US9026M08126
Tax considerations:	The United States federal income tax consequences of your
investment in the Trigger PLUS 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-33 of the
accompanying product supplement and discuss the tax consequences of your particular situation with your tax advisor. There are no statutory provisions, regulations, published rulings
or judicial decisions addressing the characterization for U.S. federal income tax purposes of Trigger PLUS with terms that are substantially
the same as the Trigger PLUS. Pursuant to the terms of the Trigger PLUS, UBS and you agree, in the absence of an administrative or
judicial ruling to the contrary, to characterize your Trigger PLUS as a pre-paid derivative contract with respect to the underlying
index. If your Trigger PLUS are so treated, if you hold your Trigger PLUS for more than one year you should generally recognize long-term
capital gain or loss upon the sale or maturity of your Trigger PLUS in an amount equal to the difference between the amount you receive
at such time and the amount you paid for your Trigger PLUS. In the opinion of our counsel, Cadwalader, Wickersham &
Taft LLP, it would be reasonable to treat your Trigger PLUS in the manner described above. However, because there is no authority
that specifically addresses the tax treatment of the Trigger PLUS, it is possible that your Trigger PLUS could alternatively be treated
for tax purposes in the manner described under ‘‘Supplemental U.S. Tax Considerations — Alternative Treatments’’
on page PS-34 of the accompanying product supplement. The Internal Revenue Service, for example, might assert that
you should be required to recognize taxable gain on any rebalancing or rollover of the underlying index. In 2007, the Internal Revenue Service released a notice that
may affect the taxation of holders of the Trigger PLUS. According to the notice, the Internal Revenue Service and the Treasury Department
are actively considering whether the holder of an instrument similar to the Trigger PLUS should be required to accrue ordinary income
on a current basis, and they are seeking taxpayer comments on the subject. 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 Trigger PLUS 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 of
1986, as amended (the ‘‘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 Trigger PLUS 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-33 of the accompanying
product supplement, unless and until such time as the Treasury Department and Internal Revenue Service determine that some other
treatment is more appropriate. Moreover, in 2007, legislation was introduced in Congress that,
if it had been enacted, would have required holders of Trigger PLUS purchased after the bill was enacted to accrue interest income
over the term of the Trigger PLUS despite the fact that there will be no interest payments over the term of the Trigger PLUS. 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 Trigger PLUS.

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Trigger PLUS Based on the Value of the EUROSTOXX 50 Index due July 22, 2015

| | Recent Legislation Beginning in 2013, United States 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 Trigger PLUS,
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. Under recently enacted legislation, individuals (and to the
extent provided in future regulations, entities) that own ′′specified foreign financial assets’’ in excess
of an applicable threshold may be required to file information with respect to such assets with their income 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 Trigger PLUS. Non-United States Holders. If you are not a United States
holder, you will generally not be subject to United States withholding tax with respect to payments on your Trigger PLUS and you
should not be subject to generally applicable information reporting and backup withholding requirements with respect to payments
on your Trigger PLUS if you comply with certain certification and identification requirements as to your foreign status including
providing a validly executed Internal Revenue Service Form W-8 BEN. Gain from the sale or exchange of a security or settlement
at maturity generally will not be subject to U.S. tax unless such gain is effectively connected with a trade or business conducted
by the non-United States holder in the United States or unless the non-U.S. holder is a non-resident alien individual and is present
in the U.S. for 183 days or more during the taxable year of such sale, exchange or settlement and certain other conditions are
satisfied. PROSPECTIVE PURCHASERS OF TRIGGER PLUS SHOULD CONSULT THEIR TAX
ADVISORS AS TO THE U.S. FEDERAL, STATE, LOCAL AND OTHER TAX CONSEQUENCES TO THEM OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF
THE TRIGGER PLUS. |
| --- | --- |
| Trustee: | U.S. Bank Trust National Association |
| Calculation agent: | UBS Securities LLC, a wholly-owned subsidiary of UBS AG |
| Use of proceeds and hedging: | We will use the net proceeds we receive from the sale of the
Trigger PLUS for the purposes we describe in the accompanying prospectus under “Use of Proceeds.” We or our affiliates
may also use those proceeds in transactions intended to hedge our obligations under the Trigger PLUS as described below. |
| | In connection with the sale of the Trigger PLUS, we or our affiliates may enter into hedging transactions involving the execution of long-term or short-term interest rate swaps, futures and option transactions or purchases and sales of Trigger PLUS before and after the pricing date of the Trigger PLUS. From time to time, we or our affiliates may enter into additional hedging transactions or unwind those we have entered into. |
| Supplemental information regarding plan of distribution; conflicts of interest: | Pursuant to the terms of a distribution agreement, UBS has agreed
to sell to UBS Securities LLC, and UBS Securities LLC has agreed to purchase from UBS, the stated principal amount of the Trigger PLUS
specified on the front cover of this document. UBS Securities LLC, acting as agent for UBS, will receive a fee of $0.30 per $10.00
stated principal amount of Trigger PLUS and will pay the entire fee to Morgan Stanley Smith Barney LLC as a fixed sales commission
of $0.30 for each $10.00 stated principal amount of Trigger PLUS that Morgan Stanley Smith Barney LLC sells. 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 Trigger PLUS.
UBS Securities LLC and/or its affiliates may earn additional income as a result of payments pursuant to these swap or related hedge
transactions. UBS, UBS Securities LLC or any other affiliate of UBS may use
this document, the accompanying product supplement and the accompanying prospectus in a market-making transaction for any Trigger PLUS
after their initial sale. In connection with this offering, UBS, UBS Securities LLC, any other affiliate of UBS or any other securities
dealers may distribute this document, the accompanying product supplement and the accompanying prospectus electronically. Unless
UBS or its agent informs the purchaser otherwise in the confirmation of sale, this document, the accompanying product supplement
and the accompanying prospectus are being used in a market-making transaction. |

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Conflicts of Interest — UBS Securities LLC 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 Trigger PLUS and, thus creates an additional conflict of interest within the meaning of FINRA Rule 5121. Consequently, the offering is being conducted in compliance with the provisions of Rule 5121.

Contact:

Morgan Stanley Smith Barney clients may contact their local Morgan Stanley Smith Barney branch office or its principal executive offices at 1585 Broadway, New York, New York 10036 (telephone number (866) 477-4776). All other clients may contact their local brokerage representative.

Selling concessions allowed to dealers in connection with the offering may be reclaimed by the agent, if, within 30 days of the offering, the agent repurchases the Trigger PLUS distributed by such dealers.

This pricing supplement represents a summary of the terms and conditions of the Trigger PLUS. We encourage you to read the accompanying product supplement and prospectus related to this offering, which can be accessed via the hyperlinks on page 2 of this document.

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How the Trigger PLUS Work

Payoff Diagram

The payoff diagram below illustrates the payment at maturity on the Trigger PLUS for a range of hypothetical percentage changes in the closing value of the underlying index.

Investors will not be entitled to receive any dividends paid with respect to the stocks that constitute the underlying index. You should carefully consider whether an investment that does not provide for dividends or periodic interest is appropriate for you. The payment scenarios below do not show any effect of lost dividend yield over the term of the Trigger PLUS.

The graph is based on the following terms:

Stated principal amount:	$10 per security
Leverage factor:	2
Trigger value:	75% of the initial index value
Minimum payment at maturity:	None

Trigger PLUS Payoff Diagram

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How it works

§ If the final index value is greater than the initial index value, investors will receive the $10 stated principal amount plus 2 times the appreciation of the underlying index over the term of the Trigger PLUS.

§ If the final index value has appreciated from the initial index value by 15%, investors will receive a 30% return, or $13.00 per security.

§ If the final index value is less than the initial index value but equal to or greater than the trigger value, investors will receive an amount equal to the $10 stated principal amount.

§ If the final index value is less than the trigger value, investors will receive an amount at least 25% less than the $10 stated principal amount, based on a 1% loss of principal for each 1% decline in the underlying index.

§ If the underlying index depreciates 35%, investors would lose 35% of their principal and receive only $6.50 per security at maturity, or 65% of the stated principal amount. There is no minimum payment at maturity on the Trigger PLUS.

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Payment at Maturity

At maturity, investors will receive for each $10 stated principal amount of Trigger PLUS that they hold an amount in cash based upon the closing value of the underlying index on the valuation date, as determined as follows:

If the final index value is greater than the initial index value:

$10 + leveraged upside payment.

| | | | Leveraged
Upside Payment | | | | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Principal | | | Principal | | Leverage
Factor | | | Index
Percent Increase | |
| $10 | + | [ | $10 | x | 2 | x | ( | final
index value – initial index value initial index value | ) ] |

If the final index value is less than the initial index value but equal to or greater than the trigger value:

the stated principal amount of $10

If the final index value is less than the trigger value:

$10 + ($10 x index performance factor

Principal — $10	+	[	Principal — $10	x	(	Index Performance Factor — final index value – initial index value initial index value	)]

Accordingly, if the final index value is below the trigger value, UBS will pay you less than the full stated principal amount, if anything, resulting in a loss on your investment that is proportionate to the negative return of the underlying index. You may lose up to 100% of your principal.

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Risk Factors

The following is a non-exhaustive list of certain key risk factors for investors in the Trigger PLUS. For further discussion of these and other risks, you should read the section entitled “Risk Factors” in the accompanying product supplement and “Risk Factors” in the related product supplement. We also urge you to consult your investment, legal, tax, accounting and other advisers in connection with your investment in the Trigger PLUS.

§ The Trigger PLUS do not pay interest or guarantee return of principal. The terms of the Trigger PLUS differ from those of ordinary debt securities in that the Trigger PLUS do not pay interest or guarantee the return of any of the stated principal amount at maturity. If the final index value is less than the trigger value (which is 75% of the initial index value), the payout at maturity will be an amount in cash that is at least 25% less than the $10 stated principal amount of security, and this decrease will be by an amount proportionate to the full amount of the decrease in the value of the underlying index from the pricing date to the valuation date. There is no minimum payment at maturity on the Trigger PLUS, and, accordingly, you could lose your entire investment.

§ The contingent repayment of principal applies only at maturity. You should be willing to hold your Trigger PLUS to maturity. If you are able to sell your Trigger PLUS prior to maturity in the secondary market, you may have to sell them at a loss relative to your initial investment even if the level of the underlying index at that time is equal to or above the initial index value.

§ Credit risk of UBS — The Trigger PLUS 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 Trigger PLUS, including 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 Trigger PLUS 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 Trigger PLUS and you could lose your entire investment.

§ The market price of the Trigger PLUS will be influenced by many unpredictable factors. Several factors will influence the value of the Trigger PLUS prior to maturity. Although we expect that generally the closing value of the underlying index on the valuation date will affect the value of the Trigger PLUS more than any other single factor, other factors that may influence the value of the Trigger PLUS include: the value and volatility (frequency and magnitude of changes in value or price) of the underlying index and the stocks that constitute the underlying index, the dividend yield of the stocks that constitute the underlying index, geopolitical conditions and economic, financial, political and regulatory or judicial events that affect the underlying index or equities markets generally and that may affect the closing value of the underlying index, interest and yield rates in the market, time remaining until the Trigger PLUS mature and any actual or anticipated changes in the credit ratings or credit spreads of UBS. The value of the underlying index may be, and has recently been, extremely volatile, and we can give you no assurance that the volatility will lessen. See "Historical Information" below. You may receive less, and possibly significantly less, than the stated principal amount of the Trigger PLUS if you try to sell your Trigger PLUS prior to maturity.

§ Owning the Trigger PLUS is not the same as owning the index constituent stocks. Owning the Trigger PLUS is not the same as owning the index constituent stocks. As a holder of the Trigger PLUS, you will not have voting rights or rights to receive dividends or other distributions or other rights that holders of the index constituent stocks would have.

§ No assurance that the investment view implicit in the Trigger PLUS will be successful. It is impossible to predict whether and the extent to which the value of the underlying index will rise or fall. There can be no assurance that the underlying index value will not close below the trigger value on the valuation date. The closing value of the underlying index will be influenced by complex and interrelated political, economic, financial and other factors that affect the issuers of the underlying index components. You should be willing to accept the risk of losing some or all of your initial investment.

§ Adjustments to the underlying index could adversely affect the value of the Trigger PLUS. The publisher of the underlying index may add, delete or substitute the stocks that constitute the underlying index or make other methodological changes that could change the value of the underlying index. The publisher of the underlying index may discontinue or suspend calculation or publication of the underlying index at any time. In these circumstances, the calculation agent will have the sole discretion to substitute a successor index that is comparable to the discontinued underlying index and is not precluded from considering indices that are calculated and published by the calculation agent or any of its affiliates.

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§ UBS cannot control actions by the publisher of the underlying index and the publisher of the underlying index has no obligation to consider your interests. UBS and its affiliates are not affiliated with the publisher of the underlying index and have no ability to control or predict its actions, including any errors in or discontinuation of public disclosure regarding methods or policies relating to the calculation of the underlying index. The publisher of the underlying index is not involved in the Trigger PLUS offering in any way and has no obligation to consider your interest as an owner of the Trigger PLUS in taking any actions that might affect the market value of your Trigger PLUS.

§ The inclusion of underwriting fees and projected profit from hedging in the original issue price is likely to adversely affect secondary market prices. Assuming no change in market conditions or any other relevant factors, the price, if any, at which UBS Securities LLC is willing to purchase the Trigger PLUS in secondary market transactions will likely be lower than the issue price, since the issue price will include, and secondary market prices are likely to exclude, underwriting fees paid with respect to the Trigger PLUS, as well as the cost of hedging our obligations under the Trigger PLUS. The cost of hedging includes the projected profit that our affiliates may realize in consideration for assuming the risks inherent in managing the hedging transactions. The secondary market prices for the Trigger PLUS are also likely to be reduced by the costs of unwinding the related hedging transaction. Our affiliates may realize a profit from the expected hedging activity even if the market value of the Trigger PLUS declines. In addition, any secondary market prices for the Trigger PLUS may differ from values determined by pricing models used by UBS Securities LLC, as a result of dealer discounts, mark-ups or other transaction costs.

§ Exchange listing and secondary market. The Trigger PLUS will not be listed on any securities exchange. Although UBS Securities LLC may make a market in the Trigger PLUS, it is not obligated to do so. Even if there is a secondary market, it may not provide enough liquidity to allow you to trade or sell the Trigger PLUS easily. Because we do not expect that other broker-dealers will participate significantly in any secondary market that may develop for the Trigger PLUS, the price at which you may be able to sell your Trigger PLUS is likely to depend on the price, if any, at which UBS Securities LLC is willing to transact. If, at any time, UBS Securities LLC were not to make a market in the Trigger PLUS, it is likely that there would be no secondary market for the Trigger PLUS. Accordingly, you should be willing to hold your Trigger PLUS to maturity.

§ The Trigger PLUS are subject to currency exchange rate risk. The EURO STOXX 50 ® Index invests in securities that are traded and quoted in foreign currencies on non-U.S. markets. Therefore, holders of the Trigger PLUS will be exposed to currency exchange rate risk with respect to the currencies in which such securities trade. Although the stocks underlying the index are traded in euro s and your Trigger PLUS are denominated in U.S. dollars, the amount payable on your Trigger PLUS at maturity will not be adjusted for changes in the U.S. dollar foreign currency exchange rates relating to the index stocks. The payment amount on the Trigger PLUS will be based solely upon the overall change in the value of the index from the trade date to the valuation date. Changes in the U.S. dollar/ European Union euro exchange rate, however, may reflect changes in the European Union or U.S. economies that, in turn, may affect the final index value. The values of the currencies of the countries in which the EURO STOXX 50 ® Index may invest may be subject to a high degree of fluctuation due to changes in interest rates, the effects of monetary policies issued by the United States, foreign governments, central banks or supranational entities, the imposition of currency controls or other national or global political or economic developments. An investor’s net exposure will depend on the extent to which the relevant non-U.S. currencies strengthen or weaken against the U.S. dollar and the relative weight of each non-U.S. security in the portfolio of the EURO STOXX 50 ® Index. If, taking into account such weighting, the U.S. dollar strengthens against the relevant non-U.S. currencies, the value of securities in which the EURO STOXX 50 ® Index invests will be adversely affected and the value of the Trigger PLUS may decrease.

§ The Trigger PLUS are subject to non-U.S. securities market risk. The underlying index constituent stocks that comprise the EURO STOXX 50 ® Index are issued by non-U.S. companies in non-U.S. securities markets. An investment in Trigger PLUS linked directly or indirectly to the value of securities issued by non-U.S. companies involves particular risks. Generally, non-U.S. securities markets may be more volatile than U.S. securities markets, and market developments may affect non-U.S. markets differently from U.S. securities markets. Direct or indirect government intervention to stabilize these non-U.S. markets, as well as cross shareholdings in non-U.S. companies, may affect trading prices and volumes in those markets. There is generally less publicly available information about non-U.S. companies than about those U.S. companies that are subject to the reporting requirements of the SEC, and non-U.S. companies are subject to accounting, auditing and financial reporting standards and requirements that differ from those applicable to U.S. reporting companies. Securities prices in non-U.S. countries are subject to political, economic, financial and social factors that may be unique to the particular country. These factors, which could negatively affect the non-U.S. securities markets, include the possibility of recent or future changes in the non-U.S. government’s economic and fiscal policies, the possible imposition of, or changes in, currency exchange laws or other non-U.S. laws or restrictions applicable to non-U.S. companies or investments in non-U.S. equity securities. Moreover, certain aspects of a particular non-U.S. economy may differ favorably or unfavorably from the U.S. economy in important respects, such as growth of gross national product, rate of inflation, capital reinvestment, resources and self-sufficiency. Finally, it will likely be more costly and difficult to enforce the laws or regulations of a non-U.S. country or exchange. All of these factors could have a material adverse effect on the value of the Trigger PLUS.

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§ Potential conflict of interest. UBS and its affiliates may engage in business related to the underlying index or index constituent stocks, which may present a conflict between the obligations of UBS and you, as a holder of the Trigger PLUS. The calculation agent, an affiliate of the issuer, will determine the final index value and the payment at maturity based on the closing value of the underlying index on the valuation date. The calculation agent can postpone the determination of the final index value or the maturity date if a market disruption event occurs and is continuing on the valuation date.

§ Affiliate research reports and commentary . UBS and its affiliates publish research from time to time on financial markets and other matters that may influence the value of the Trigger PLUS, or express opinions or provide recommendations that are inconsistent with purchasing or holding the Trigger PLUS. 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 Trigger PLUS and the underlying index to which the Trigger PLUS are linked.

§ Hedging and trading activity by the calculation agent and its affiliates could potentially affect the value of the Trigger PLUS. One or more of our affiliates have hedged our obligations under the Trigger PLUS and will carry out hedging activities related to the Trigger PLUS (and other instruments linked to the underlying index or the stocks that constitute the underlying index), including trading in stocks that constitute the underlying index, swaps, futures and options contracts on the underlying index as well as in other instruments related to the underlying index and the stocks that constitute the underlying index. Our affiliates also trade in the stocks that constitute the underlying index and other financial instruments related to the underlying index and the stocks that constitute the underlying index on a regular basis as part of their general broker-dealer, proprietary trading and other businesses. Any of these hedging or trading activities on or prior to the pricing date could have potentially increased the initial index value and, as a result, could have increased the value at which the underlying index must close on the valuation date so that investors do not suffer a loss on their initial investment in the Trigger PLUS. Additionally, such hedging or trading activities during the term of the Trigger PLUS, including on the valuation date, could adversely affect the value of the underlying index on the valuation date and, accordingly, the amount of cash, if any, an investor will receive at maturity.

§ Uncertain tax treatment — Significant aspects of the tax treatment of the Trigger PLUS are uncertain. You should read carefully the section entitled ‘‘Tax considerations’’ on page 6 herein and the section entitled ‘‘Supplemental U.S. Tax Considerations’’ beginning on page PS-33 of the accompanying product supplement and consult your tax advisor about your tax situation.

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EURO STOXX 50 ® Index Overview

The EURO STOXX 50 ® Index was created by STOXX ® Limited, which is owned by Deutsche Börse AG and SIX Group AG. Publication of the EURO STOXX 50 ® Index began on February 26, 1998, based on an initial index value of 1,000 at December 31, 1991. The EURO STOXX 50 ® Index is composed of 50 component stocks of market sector leaders from within the STOXX 600 Supersector Indices, which includes stocks selected from the Eurozone. The component stocks have a high degree of liquidity and represent the largest companies across all market sectors. For additional information about the EURO STOXX 50 ® Index, see the information set forth under “EURO STOXX 50 ® Index” in the accompanying index supplement.

Information as of market close on April 27, 2012:

Bloomberg Ticker Symbol:	SX5E
Current Index Value:	2344.02
52 Weeks Ago (on 4/27/11):	2977.59
52 Week High (on 4/29/11):	3011.25
52 Week Low (on 9/12/11):	1995.01

The following graph sets forth the daily closing values of the underlying index for the period from January 1, 2007 through April 27, 2012. The related table sets forth the published high and low closing values, as well as end-of-quarter closing values, of the underlying index for each quarter in the same period. The closing value of the underlying index on April 27, 2012 was 2344.02. We obtained the information in the table and graph below from Bloomberg Financial Markets, without independent verification. We make no representation or warranty as to the accuracy or completeness of the information obtained from Bloomberg. The historical values of the underlying index should not be taken as an indication of future performance, and no assurance can be given as to the value of the underlying index on the valuation date.

Underlying Index Historical Performance – Daily Closing Values From January 1, 2007 to April 27, 2012

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Historical Information

The following table sets forth the published high and low closing values, as well as the end-of-quarter closing values, of the underlying index for each quarter in the period from January 1, 2007 through April 27, 2012. The closing value of the underlying index on April 27, 2012 was 2344.02. We obtained the information in the table below from Bloomberg Financial Markets, without independent verification. We make no representation or warranty as to the accuracy or completeness of the information obtained from Bloomberg. The historical closing values of the underlying index should not be taken as an indication of future performance, and no assurance can be given as to the closing value of the underlying index on the valuation date.

| EURO
STOXX 50 ® Index | High | Low | Period End |
| --- | --- | --- | --- |
| 2007 | | | |
| First Quarter | 4,272.32 | 3,906.15 | 4,181.03 |
| Second Quarter | 4,556.97 | 4,189.55 | 4,489.77 |
| Third Quarter | 4,557.57 | 4,062.33 | 4,381.71 |
| Fourth Quarter | 4,489.79 | 4,195.58 | 4,399.72 |
| 2008 | | | |
| First Quarter | 4,339.23 | 3,431.82 | 3,628.06 |
| Second Quarter | 3,882.28 | 3,340.27 | 3,352.81 |
| Third Quarter | 3,445.66 | 3,000.83 | 3,038.20 |
| Fourth Quarter | 3,113.82 | 2,165.91 | 2,447.62 |
| 2009 | | | |
| First Quarter | 2,578.43 | 1,809.98 | 2,071.13 |
| Second Quarter | 2,537.35 | 2,097.57 | 2,401.69 |
| Third Quarter | 2,899.12 | 2,281.47 | 2,872.63 |
| Fourth Quarter | 2,992.08 | 2,712.30 | 2,964.96 |
| 2010 | | | |
| First Quarter | 3,017.85 | 2,631.64 | 2,931.16 |
| Second Quarter | 3,012.65 | 2,488.50 | 2,573.32 |
| Third Quarter | 2,827.27 | 2,507.83 | 2,747.90 |
| Fourth Quarter | 2,890.64 | 2,650.99 | 2,792.82 |
| 2011 | | | |
| First Quarter | 3,068.00 | 2,721.24 | 2,910.91 |
| Second Quarter | 3,011.25 | 2,715.88 | 2,848.53 |
| Third Quarter | 2,875.67 | 1,995.01 | 2,179.66 |
| Fourth Quarter | 2,476.92 | 2,090.25 | 2,316.55 |
| 2012 | | | |
| First Quarter | 2608.42 | 2286.45 | 2477.28 |
| Second Quarter (through April 27, 2012) | 2501.18 | 2244.83 | 2344.02 |

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