NOTICE TO THE MARKET Offer Stabilization Agent Rio de Janeiro, Brazil, Decemberr December r 07, 2010 – HRT Participações em Petróleo S.A. (the “Company” or “HRT”), in compliance with the provisions of Article 12 of CVM Instruction 358/02, informs the acceptance of the attached letter from Banco de Investimentos Credit Suisse (Brasil) S.A., as shareholder of HRT, communicating the acquisition in 11/25/2010 of a total of 118,300 common shares of the Company (2.561%), holding a total amounting of 5.260% HRT’s voting capital on such date and the disposal in 11/26/2010 of a total of 243,000 common shares of the Company, which represents 5.260% of HRT’s voting capital. Further, according to information provided by Banco de Investimentos Credit Suisse (Brasil) S.A., the acquisition, just as the disposal, took place within the context of stabilization activities related to the primary and secondary tender offer of the Company shares (“Offer”). The buyer/seller was the offer stabilization agent. Attached is the original letter sent by Banco de Investimentos Credit Suisse (Brasil) S.A. and a free translation to portuguese. For further information, contact HRT’s Investor Relations Department. About HRT Participações HRT Participações holds one of the largest independent oil and gas exploration and production companies in Brazil. The HRT Group comprises three main subsidiaries: IPEX (Integrated Petroleum Expertise Company Serviços em Petróleo Ltda.), HRT O&G Exploração e Produção de Petróleo Ltda. and HRT Netherlands B.V. The Company retains a 55% interest in 21 exploratory blocks in the Solimões Basin. HRT also operates five exploratory blocks at the Namibian coast,. The Company retains a 100% interest in two of them, in the Walvis Sub-basin, and a 40% interest in the other three, in the Orange Subbasin. HRT’s team includes PHDs and masters in geochemistry, geophysics, biology and engineering, most of them former employees of Petrobras and ANP (Brazil’s petroleum agency). HRT is committed to minimizing any possible environmental impacts in the sites where it acts. Our commitment with the local communities is towards health conditions, security and quality of life. For more information, please visit the Company’s website: www.hrt.com.br/ir BANCO DE INVESTIMENTOS CREDIT SUISSE (BRASIL) S.A. FREE TRANSLATE TO ENGLISH Av. Brig. Faria Lima, 3064 / 13º São Paulo - SP 01451-000 Phone: (55 11) 3841.6000 Fax: (55 11) 3841.6900 São Paulo, December 03, 2010. To HRT Participações em Petróleo S.A. Av. Atlântica nº 1130 - 10º andar (parte) 22021-000 – Rio de Janeiro – RJ Attn.: Mr. Márcio Rocha Mello Investor Relations Officer Copy to: Mrs. Eliana Soares Rodrigues Investor Relations Manager Re: Acquisition and Disposal of Relevant Interest in the Tender Offer Stabilization Process –CVM Rule 358/02 Dear Sirs, In compliance with the provisions of Article 12 of the CVM Rule 358/02 and CMN Resolution 2689/00 (“CMN Resolution 2689”), please find below the information about the acquisition and disposal of relevant interest of common shares issued by HRT Participações em Petróleo S.A. (“Shares” and “Company”, respectively): On November 25, 2010, the Buyer/Seller (identified herein below) acquired 118,300 shares (corresponding approximately to 2.63% of total shares) (“Acquisition”), holding a total amounting on such date of 5,40% shares. Subsequently, November 26, 2010, the Buyer/Seller disposed of 243,000 shares (corresponding approximately to 5.40% of total shares) (“Disposal”), with wich ceased to hold any more shares. The Acquisition, just as the Disposal, took place within the context of stabilization activities related to the primary and secondary tender offer of the Company shares (“Offer”). The Buyer/Seller was the Offer stabilization agent. I. name and identification of the Buyer/Seller: Banco de Investimentos Credit Suisse (Brasil) S.A., headquartered in the City and State of São Paulo, at Av. Brigadeiro Faria Lima, 3064, 12º, 13º a 14º andares (parte), duly registered at the corporate taxpayer’s ID (CNPJ/MF) 33.987.793/0001-33 (“Buyer/Seller”). BANCO DE INVESTIMENTOS CREDIT SUISSE (BRASIL) S.A. FREE TRANSLATE TO ENGLISH Av. Brig. Faria Lima, 3064 / 13º São Paulo - SP 01451-000 Phone: (55 11) 3841.6000 Fax: (55 11) 3841.6900 II. purpose of interest and amount intended, including, if this is the case, a statement of the Buyer/Seller reiterating that acquisitions neither aimed at changing the Company’s ownership structure nor its administrative structure: The Acquisition and the Disposal took place within the context of the Offer stabilization process, thus, they neither aimed at changing the Company’s ownership structure nor its administrative structure. III. number of shares, warrants, as well as subscription rights and stock options, by type and class, already directly or indirectly held by Buyer/Seller or related party: The Buyer/Seller is aware that (i) the investment portfolio Credit Suisse Securities (Europe) Limited (Res. CMN 2689), a company headquartered at One Cabot Square, E14, 4QJ, London, United Kingdom, corporate taxpayer’s ID (CNPJ/MF) 09.255.004/0001-95, represented in Brazil by Credit Suisse (Brasil) S.A. Corretora de Títulos e Valores Mobiliários on November 26,2010 held 27,700 shares (corresponding approximately to 0.61% of total shares); and (ii) that the investment portfolio Credit Suisse Securities (Europe) Limited (CMN Resolution 2689), a company headquartered at One Cabot Square, E14, 4QJ, London, United Kingdom, corporate taxpayer’s ID (CNPJ/MF) 06.541.158/0001-55, represented in Brazil by Credit Suisse (Brazil) Distribuidora de Títulos e Valores Mobiliários S.A. on November 26, 2010 held 330 Shares (corresponding approximately to 0.007% of total shares). With the exception of the aforementioned paragraph, at this present time, the Buyer/Seller is not aware of any related party to hold shares, warrants, subscription rights and/or stock options for the Company shares. IV. number of debentures convertible into shares, already directly or indirectly held by Acquirer/Seller or related party, explaining the amount of shares, purpose of a potential conversion, by type and class: The Buyer/Seller is not aware of any related party to hold debentures convertible into the Company shares. V. indication of any agreement or contract regulating the exercise of the voting right or the purchase and sale of the Company securities: The Buyer/Seller does not have this type of agreement. BANCO DE INVESTIMENTOS CREDIT SUISSE (BRASIL) S.A. FREE TRANSLATE TO ENGLISH Av. Brig. Faria Lima, 3064 / 13º São Paulo - SP 01451-000 Phone: (55 11) 3841.6000 Fax: (55 11) 3841.6900 Finally, we request you to immediately forward the content of this letter to the Brazilian Securities and Exchange Commission – CVM and to São Paulo Stock Exchange, according to Article 12, Paragraph 6 of CVM Rule 358/02. We remain available for any further information you may deem necessary. Yours faithfully, ____________________________________________________________________ Banco de Investimentos Credit Suisse (Brasil) S.A.