Investment Agreement with Petrobras

Buenos Aires, 5 de agosto de 2010

To:
BUENOS AIRES STOCK EXCHANGE

ARGENTINE SECURITIES COMISSION

Your Offices

Ref.: Relevant Event. Pampa Energía
and Petrobras partner to develop new
wells in Neuquén

Dear Sirs,

In my capacity as Responsible of Market Relations for Pampa Energía S.A. (“Pampa” or the “Company”), I am pleased to inform the Argentine Securities Commission and the Buenos Aires Stock Exchange that on December 7, 2010, Pampa, through its subsidiary Petrolera Pampa S.A., has entered into an investment agreement with Petrobras Argentina S.A. (“Petrobras”) for the “El Mangrullo” field located in the province of Neuquén, under which Pampa will acquire, subject to the fulfillment of certain conditions precedent, 43% of the right to freely dispose at wellhead, to commercialize and to process the hydrocarbons obtained from wells to be drilled in the field mentioned above (the “Wells”).

As a consideration for said acquisition, Pampa has committed to invest up to U$S 16,000,000 on the drilling of those Wells.

The parties estimate to obtain a total natural gas production of 400,000 m3/day from the Wells under Gas Plus Program, which will be allocated to the supply of Central Térmica Loma de la Lata.

Moreover, the parties are negotiating a 400,000 m3/day Gas Plus contract, which is one of the yet-to-be-fulfilled precedent conditions to the investment agreement described above.

With this initiative and those previously announced, the Company estimates that it has guaranteed the full gas supply of Central Térmica Loma de la Lata.

Sincerely,

Romina Benvenuti
Responsible of Market Relations