Endeavour Continues Successful Appraisal Drilling in Cygnus Field

HOUSTON - Endeavour International Corporation (NYSE-Alt: END) (LSE: ENDV) today announced that the Cygnus 44/12a-4 appraisal well in the Southern Gas Basin in the North Sea has further extended the productive area of the Cygnus field by confirming the presence of recoverable gas reserves in a third fault block. Endeavour holds a 12.5 percent interest in the Cygnus field area spread over two United Kingdom blocks, 44/11a and 12a. License partners include GDF SUEZ, the operator, and Venture Production plc.

The well was drilled to a total depth of 12,284 feet and flow tested at a rate of 32 million cubic feet of gas per day from the targeted Rotliegendes Leman reservoir. Endeavour estimates that gross recoverable reserves from the eastern portion of the field alone will be in excess of 500 billion cubic feet. This number is expected to increase as additional fault blocks are drilled.

“The results of appraisal drilling in the Cygnus field continue to surpass our expectations. We believe the area will prove to be one of the largest natural gas fields to be discovered in the Southern Gas Basin in the last decade,” said William L. Transier, chairman and chief executive officer. “The Cygnus field, combined with the Rochelle and Columbus developments, comprise the three major natural gas projects in the United Kingdom that will provide the company substantial growth in production over the next few years.”

A revised field development plan for Cygnus was submitted to the United Kingdom governing authority, Department of Energy and Climate Change, in March, 2009 and contained a phased development scenario that called for initial production to begin in the fourth quarter of 2010.

Endeavour International Corporation is an oil and gas exploration and production company focused on the acquisition, exploration and development of energy reserves in the North Sea and the United States. For more information, visit www.endeavourcorp.com

Certain statements in this news release should be regarded as “forward-looking” statements within the meaning of the securities laws. These statements speak only as of the date made. Such statements are subject to assumptions, risk and uncertainty. Actual results or events may vary materially.

Source: Endeavour International Corporation

UK Investors, Jeffrey Auld of Cannacord Adams, +44(0)207-050-650; or UK Media, Philip Dennis, +44(0)207-743 6363, or Henry Lerwill, +44(0)203-178-6242, both of Pelham Public Relations, all for Endeavour International Corporation; or Mike Kirksey, Investor Relations of Endeavour International Corporation, +44(0)207-451-2360, or +1-713-307-8788