Endeavour Reports Positive Results From US Drilling Initiative

Encouraging flow tests recorded from recent wells drilled in the Haynesville, Cotton Valley and Marcellus gas plays.

HOUSTON, June 21, 2010 - Endeavour International Corporation (NYSE Amex: END) (LSE: ENDV)
announced today that its drilling program in the United States is recording
encouraging test results from joint-interest wells in the Haynesville, Cotton
Valley and Marcellus gas plays. The new initiative is part of the company's
strategy to establish a growth-oriented portfolio of domestic onshore
properties that complement its development and producing assets in the United
Kingdom.

"Initial drilling results support our belief that our move into emerging
US gas shale and frontier plays will serve as a predictable and sustainable
source of reserves and production for our company in the future," said
William L. Transier, chairman, chief executive officer and president. "We are
especially pleased with excellent test results from our first well in the
Haynesville area where the company and our partner have a large acreage
position that will allow us to capitalize on opportunities in the region."

Haynesville Play, Louisiana

At the Woodardville Field in Red River and Bienville Parishes, Louisiana,
the J-W Operating Company-operated Batchelor 3-1H horizontal Haynesville well
tested gas at an initial rate of 21.5 million cubic feet per day (mmcfd) from
a 24/64-inch choke at a flowing pressure of 7,732 pounds per square inch. The
Batchelor well is a direct east offset to the Indigo Minerals 3-1H horizontal
Haynesville completion that has produced more than three billion cubic feet
of gas in the past year. Endeavour holds a 50 percent working interest in
both the Batchelor and Indigo Minerals wells. The company also has a 41.5
percent interest in the Woodard 10-1H horizontal Haynesville test currently
being drilled as a southern offset to the Batchelor and Indigo Minerals
wells. In addition, Endeavour has minority interests in three
outside-operated Haynesville tests in the Woodardville Field and one
outside-operated well in the Grand Cane Field, DeSoto Parish, all of which
are at various stages of drilling or completion.

Endeavour holds approximately 13,500 gross acres in the highly productive
Louisiana portion of the proven Haynesville shale gas play in a 50/50 joint
venture with Cohort Energy with over 200 gross potential future locations.

Lower Cotton Valley Play, East Texas

At the East Willow Springs Field in Gregg County, Texas, the J-W
Operating Company-operated Longview North Gas Unit 1H horizontal Cotton
Valley Sand well tested gas at an initial rate of 6,144 thousand cubic feet
per day (mcfd) from a 28/64-inch choke at a flowing pressure of 2,525 pounds
per square inch. Endeavour has a 50 percent working interest in the Longview
well with up to six additional horizontal offset locations in the Lower
Cotton Valley Taylor Sandstone reservoir. The company also holds deep rights
for the Bossier and Haynesville shale plays in the area which could hold
future potential as deeper gas development continues in East Texas.

Marcellus Play, Pennsylvania

At the Daniel Prospect in Cameron County, Pennsylvania, the J-W Operating
Company-operated Pardee & Curtin Lumber Co. C-9H horizontal Marcellus
completion tested gas at an initial rate of 2,688 thousand cubic feet per day
(mcfd) through a 30/64-inch choke at a flowing pressure of 1039 pounds per
square inch. The company has a 50 percent working interest in the 9H well and
approximately 22,937 gross acres in the Daniel Prospect area. Cohort Energy
and Endeavour are currently working on an integrated development plan which
would expand existing gathering facilities and enable full development of
their joint acreage. Overall, the J-W/END joint venture has an interest in
approximately 40,000 gross acres in the Pennsylvania Marcellus Shale play
with over 300 gross potential future locations.

"We expect to continue a one rig program in the Haynesville and to drill
three more Marcellus wells this year," said Jim Emme, executive vice
president, North America. "These efforts should result in significant
production and reserve impact in 2010."

The company also plans to continue its activities in two frontier shale
plays in Alabama and Montana. In Alabama, the first of two vertical pilot
tests has commenced drilling.

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. 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)207-451-2364, +1-713-307-8788; or UK Media, Philip Dennis, +44(0)207-743-6363, or Henry Lerwill, +44(0)203-178-6242, both of Pelham Public Relations for Endeavour