ATP Marks Two Deepwater Exploration Discoveries.

HOUSTON -- ATP Oil & Gas Corporation (NASDAQ:ATPG) recently participated in the drilling of two successful exploration wells in the deepwater Gulf of Mexico. The Gladden Prospect, located at Mississippi Canyon 800 in approximately 3,116' of water, found 80 feet of net oil pay. An updip location is being drilled that is expected to be completed in late May. The Anduin West Prospect, located at Mississippi Canyon 754 in approximately 2,696' of water, found 30 feet of net gas and condensate pay. The Anduin West well is being completed and a production test is planned for next week. ATP has a 10% working interest in Gladden and a 25 % working interest in Anduin West. Newfield Exploration Company is the operator of both discoveries. ATP has production handling agreements in place for its ATP Innovator moored at Mississippi Canyon 711 "Gomez" to process the oil and gas from both locations, and production is expected to begin in late 2009.

T. Paul Bulmahn, ATP's Chairman and President said, "The future production and reserves associated with these discoveries are not included in our current reserve report. These properties also provide committed third party production to be processed for a fee by our ATP Innovator, enhancing the value of that asset. Clearly, these two discoveries validate our deepwater Hub concept, and we presently plan to drill three future wells at the Gomez Hub."

About ATP Oil & Gas Corporation

ATP Oil & Gas is an international offshore oil and gas development and production company with operations in the Gulf of Mexico and the North Sea. The company trades publicly as ATPG on the NASDAQ Global Select Market. For more information about ATP Oil & Gas Corporation, visit www.atpog.com.

Forward-looking Statements

Certain statements included in this news release are "forward-looking statements" under the Private Securities Litigation Reform Act of 1995. ATP cautions that assumptions, expectations, projections, intentions, or beliefs about future events may, and often do, vary from actual results and the differences can be material. Some of the key factors which could cause actual results to vary from those ATP expects include changes in natural gas and oil prices, the timing of planned capital expenditures, availability of acquisitions, uncertainties in estimating proved reserves and forecasting production results, operational factors affecting the commencement or maintenance of producing wells, the condition of the capital markets generally, as well as our ability to access them, and uncertainties regarding environmental regulations or litigation and other legal or regulatory developments affecting our business. More information about the risks and uncertainties relating to ATP's forward-looking statements are found in our SEC filings.