Endeavour Reports Fourth Cygnus Appraisal Success

Cygnus gas field reserve estimates continue to grow

HOUSTON, April 15, 2010 - Endeavour International Corporation (NYSE Amex: END) (LSE: ENDV) today
announced successful appraisal drilling in the western area of the Cygnus gas
field in block 44/11a has led to increased reserves and prospective resource
estimates and extended the field boundary to the north and west. Preliminary
estimates of Cygnus reserves and prospective resources could potentially be
as high as 2 trillion cubic feet of gas based on new well information making
Cygnus one of the largest gas fields ever discovered in the United Kingdom
sector of the southern North Sea.

"This significant extension of the Cygnus field allows us to develop the
area with a simplified, compressed, and lower-cost development and higher
initial production rates that will accelerate to peak production levels more
quickly," said William L. Transier, chairman, chief executive officer and
president. "This very positive increase in Cygnus reserves is another
indication of the underlying value of our UK portfolio of assets."

The 44/11a-4 well was drilled to a depth of 12,207 feet vertical depth
subsea, encountered a high quality, gas-saturated Leman sand reservoir 54
feet high to prognosis with a sand thickness of 130 feet gross and 85 feet
net. The well was flow tested at a rate of 28 million cubic feet of gas per
day.

The discovery well and five appraisal wells drilled in the Cygnus field
support a common field-wide gas water contact within approximately 10 feet
with the exception of the 44/11-2 well in the extreme southwest.

When operations cease on this well, the rig will be mobilized to the
southern part of the Cygnus field to drill a sixth well, the 44/12a-E
appraisal well. The Cygnus group plans to acquire a new field-wide 3-D
seismic survey covering the expanded boundaries of the field.

Endeavour holds a 12.5 percent interest in blocks 44/11a and 12a. License
partners are GDF Suez E&P, the operator, and Centrica.

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 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. The estimates of recoverable resources per well and completed
well costs included herein are based upon other typical results in these
shale plays and may not be indicative of actual results.

Investor Relations, Mike Kirksey, of Endeavour, +44 (0)207-451-2381, +1-713-307-8788; or UK Broker, Jeffrey Auld of Canaccord Adams, +44 (0) 207-050-6500, for Endeavour International Corporation; or UK Media, Philip Dennis, +44 (0) 20-7337-1516, or Henry Lerwill, +44 (0) 20-7337-1526, both of Pelham Bell Pottinger, for Endeavour International Corporation