SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer
Pursuant to Rule 13a-16 or 15d-16 of the

Securities Exchange Act of 1934

For the month of May, 2012

Commission File Number 1-15106

PETRÓLEO BRASILEIRO S.A. - PETROBRAS

(Exact name of registrant as specified in its charter)

Brazilian Petroleum Corporation - PETROBRAS

(Translation of Registrant's name into English)

Avenida República do Chile, 65
20031-912 - Rio de Janeiro, RJ
Federative Republic of Brazil

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F. 

Form 20-F ___X___ Form 40-F _______

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes _______ No___X____

This report on Form 6-K is incorporated by reference in the Registration
Statement on Form F-3 of Petróleo Brasileiro -- Petrobras (No. 333-163665).

 

PETRÓLEO BRASILEIRO S.A. - PETROBRAS

MATERIAL FACT

Payment of interest on own capital

Rio de Janeiro, May 28^th, 2012 – Petróleo Brasileiro S.A - Petrobras announces that it will pay the first installment of advanced payment of interest on own capital (IOC) related to the 2012 fiscal year, on May 31^st, 2012. The payment will be under the form of interest on capital, in the amount of R$ 0.20 per common (ON) or preferred (PN) shares (R$ 0.40 per ADRs), based on shareholder position at May 11^th, 2012 and in accordance to notice to shareholders issued on April 27^th, 2012.

This interest on own capital will be offset against the remuneration (dividends plus interest on own capital) to be paid related to the 2012 fiscal earnings.

This IOC (R$ 0.20) will be subject to withhold income tax of 15% (fifteen per cent).

Payment in connection with the American Depositary Receipts (ADRs) traded on the New York Stock Exchange - NYSE will be made through Bank of New York Mellon, depositary bank for the ADRs.

The expected payment date for the ADRs holders is June 7^th, 2012. Additional information may be obtained at www.adrinform.com 

Rights to IOC unclaimed within 3 (three) years as from payment date (May 31^st , 2012) will lapse and revert in favor of the Company (Law 6404/76, Article 287, Subsection II, Item a).

Almir Guilherme Barbassa

CFO and Investor Relations Officer

Petróleo Brasileiro S.A. – Petrobras

www.petrobras.com.br/ri

Para mais informações: PETRÓLEO BRASILEIRO S. A. – PETROBRAS

Relacionamento com Investidores I E-mail: petroinvest@petrobras.com.br / acionistas@petrobras.com.br

Av. República do Chile, 65 - 2202 - B - 20031-912 - Rio de Janeiro, RJI Tel.: 55 (21) 3224-1510 / 9947 I 0800-282-1540

Este documento pode conter previsões segundo o significado da Seção 27A da Lei de Valores Mobiliários de 1933, conforme alterada (Lei de Valores Mobiliários), e Seção 21E da lei de Negociação de Valores Mobiliários de 1934, conforme alterada (Lei de Negociação) que refletem apenas expectativas dos administradores da Companhia. Os termos “antecipa”, “acredita”, “espera”, “prevê”, “pretende”, “planeja”, “projeta”, “objetiva”, “deverá”, bem como outros termos similares, visam a identificar tais previsões, as quais, evidentemente, envolvem riscos ou incertezas previstos ou não pela Companhia. Portanto, os resultados futuros das operações da Companhia podem diferir das atuais expectativas, e o leitor não deve se basear exclusivamente nas informações aqui contidas.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: May 29, 2012

PETRÓLEO BRASILEIRO S.A--PETROBRAS
By:	/S/  Almir Guilherme Barbassa
	Almir Guilherme Barbassa Chief Financial Officer and Investor Relations Officer

FORWARD-LOOKING STATEMENTS

This press release may contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (Securities Act), and Section 21E of the Securities Exchange Act of 1934, as amended (Exchange Act) that are not based on historical facts and are not assurances of future results.  These forward-looking statements are based on management's current view and estimates of future economic circumstances, industry conditions, company performance and financial results. The words "anticipates", "believes", "estimates", "expects", "plans" and similar expressions, as they relate to the company, are intended to identify forward-looking statements. Statements regarding the declaration or payment of dividends, the implementation of principal operating and financing strategies and capital expenditure plans, the direction of future operations and the factors or trends affecting financial condition, liquidity or results o f operations are examples of forward-looking statements. Such statements reflect the current views of management and are subject to a number of risks and uncertainties. There is no guarantee that the expected events, trends or results will actually occur. The statements are based on many assumptions and factors, including general economic and market conditions, industry conditions, and operating factors. Any changes in such assumptions or factors could cause actual results to differ materially from current expectations. 
All forward-looking statements are expressly qualified in their entirety by this cautionary statement, and you should not place reliance on any forward-looking statement contained in this press release. We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information or future events or for any other reason.