After an account of the occurrences of oil and gas in the countries adjoining the North Sea the paper outlines the regional structural features of northwestern Europe. The outcrop geology of the North Sea floor is described and followed by an account of the stratigraphic succession in the Tertiary, Cretaceous, Jurassic, Triassic, and Permian formations. Geophysical surveys have included gravity and magnetic surveys which define the main basins, and seismic work which has shown that salt structures ranging from non-piercing salt pillows to steep-sided diapirs are developed through most of the southern North Sea. Drilling has led to discovery of three gas fields of commercial size in the basal Permian sandstone up to the time of compilation of this paper. One additional discovery since has been made in the Bunter Sandstone.