Termination of Investment Agreement with YPF

To:
BUENOS AIRES STOCK EXCHANGE
ARGENTINE SECURITIES COMISSION
Your Offices

Ref.: Investment Agreement regarding an
exploitation block known as “Rincón del
Mangrullo”

Dear Sirs,

In my capacity as Responsible of Market Relations for Pampa Energía S.A. (“Pampa” or the “Company”), I inform to the Argentine Securities Commission and to the Buenos Aires Stock Exchange regarding the relevant event published in November 19^th, 2009 about the offer from YPF S.A. (“YPF”) accepted by Petrolera Pampa S.A. (“PEPASA”), a company controlled by Pampa, to enter into an investment agreement (the “Agreement”) regarding the exploitation block known as “Rincon del Mangrullo”, located in the Province of Neuquén (the “Area”), over which YPF holds an Exploitation Concession.

We remind that, subject to the fulfillment of certain precedent conditions during a period of one year since the Agreement’s signature date (the “Period”), PEPASA would have carried out investments in the Area up to a maximum of US$ 29,000,000 in exchange for the cession by YPF of certain rights and obligations, including the right over 50% of the hydrocarbon production obtained from the geological formations in the Area subject to the Agreement.

In that sense, and in view of the lack of response to our Period postponement request for the fulfillment of the precedent conditions, the Agreement has expired.

Lastly, I take the opportunity to inform that the Company has ensured the natural gas supply of Central Térmica Loma de la Lata, which was inaugurated yesterday, through gas provision contracts under the Gas Plus program signed with Apache Argentina S.R.L., Pan American Energy Argentine Branch, among other companies.

Kind Regards,

_______________
Romina Benvenuti
Responsible of Market Relations