Pampa capital reduction

City of Buenos Aires, September 14, 2010

Messrs.
ARGENTINE SECURITIES COMMISSION
25 de Mayo 175 (CP 1002)
City of Buenos Aires, Argentina

Re.: Relevant Event – Section 2, Chapter
XXI, Book 6 of the Regulations issued by
the Argentine Securities Commission (“CNV”)

Ladies and Gentlemen,

I address the CNV in my capacity as Market Relations Officer of Pampa Energía S.A. (the “Company” or “Pampa”), in compliance with Section 2, Chapter XXI, Book 6 of the CNV’s Regulations.

In such regard, this is to give notice to you that on the date hereof the Company has been notified of CNV’s Resolution No. 16,403 which authorized the stock capital reduction and partial public offering cancellation in respect of 211,883,347 common, registered, non-endorsable shares of $1 (one peso) par value each and entitled to one vote per share held in the Company’s treasury, which had been approved by the General Extraordinary Shareholders’ Meeting dated April 23, 2010. Consequently, Pampa’s current stock capital admitted for public offering amounts to $1,314,310,895 represented by 1,314,310,895 common, registered, non-endorsable shares of $1 (one peso) par value each and entitled to 1 (one) vote per share.

Sincerely yours,

______________________
Romina Benvenuti
Market Relations Officer