Memorandum of Understanding with Petrobras

For Immediate Release

Pampa Energía enters Memorandum of Understanding with Petrobras

Buenos Aires, May 10, 2011. Pampa Energía S.A. (NYSE: PAM; Buenos Aires Stock Exchange: PAMP), announces today that it has signed a Memorandum of Understanding with Inversiones Argentina I Ltd. (“IAI”), Pampa Inversiones S.A. (“PISA”, and jointly with IAI and Pampa Energía S.A., “Pampa”), Petrobras Energía S.A. (“PESA”), Petrobras Hispano Argentina S.A. (“PHA”) and Compañía de Inversiones de Energía S.A. (“CIESA”, and jointly with Pampa, PESA and PHA, the “Parties”), in which the Parties agree: a) to suspend (“standstill”) the lawsuit titled “Compañía de Inversiones de Energía S.A. v. AEI, AEI v. Compañía de Inversiones de Energía S.A., Petrobras Energía S.A., Petrobras Hispano Argentina S.A., Héctor Daniel Casal, Claudio Fontes Nunes and Rigoberto Mejía Aravena”, currently pending before the Supreme Court of the State of New York (Index Nº 600245/09E), with the purpose of making the best efforts to reestablish the financial restructuring set forth in the Restructuring Agreement executed on September 1, 2005 between CIESA, PESA, PHA, Enron Pipeline Company Argentina S. A. (“EPCA”), ABN AMRO Bank N. V. Sucursal Argentina (acting in its capacity of trust and not on his own behalf, “ABN”) and the Financial Creditors of CIESA (hereinafter known as “Restructuring Agreement”), regarding the Bonds issued on April 22, 1997 by CIESA and the two derivative transactions originally executed between CIESA and J. Aron & Company on August 3, 2000, and between CIESA and Morgan Guaranty Trust Company of New York on August 4, 2000 (based on the debt for equity exchange described in Section 2.6 and elsewhere of said Restructuring Agreement) (the “Lawsuit”), and to include Pampa as a party of the Restructuring Agreement, subject to complying with necessary governmental approvals in order to implement the Restructuring Agreement; b) subject to obtaining the required governmental approvals, to opportunely withdraw all the claims and actions that the Parties and third parties have initiated in the Lawsuit, ending all the litigations among them.

The referred Memorandum of Understanding executed on the date hereof represents an important event in the restructuring process of CIESA’s defaulted debt , and once said restructuring is achieved through the Restructuring Agreement’s implementation, Pampa (financial creditor of CIESA) would obtain, on the one hand, 50% of CIESA’s equity, which in turn would control 51% of TGS, and on the other hand, a direct 4.3% stake of TGS. This restructuring procedure would finally end the default process to which CIESA has been subject for eight years.

For further information, contact:

Ricardo Torres – Chief Executive Officer
Mariano Batistella – Strategic Planning and Investor Relations
3302 Ortiz de Ocampo, Building #4
(C1425DSR) Ciudad Autónoma de Buenos Aires, Argentina
Phone: 5411 4809 9500
http://www.pampaenergia.com/ir
investor@pampaenergia.

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