A research conference originally scheduled as a Hedberg Research Conference examining the origins of oil and gas was held in Calgary, June 2005. This report summarizes the 14 presentations made at the conference, which discussed data and evidence regarding the abiogenic and biogenic origins of petroleum. In addition, the postpresentation discussion is summarized. Multiple concepts for the abiogenic formation of petroleum were presented. These concepts fell mostly into two broad families: mantle degassing associated with the polymerization of low molecular weight compounds and serpentization in association with Fischer-Tropsch reactions. The Fischer-Tropsch reactions are catalyzed reactions in which carbon monoxide and hydrogen are converted into hydrocarbons. The presentations on the biogenic origin presented a uniform model in which sedimentary organic matter is thermally converted to oil and gas. Little common ground was found to exist between the abiogenic and biogenic schools of petroleum formation, with the possible exception of the importance of fluid flow in controlling the formation of hydrocarbon accumulations. Although few, if any, conference participants changed their perspectives, most concluded that the meeting was informative and a useful exercise.