As geophysics has matured in recent years, its important place as a tool in oil exploration has been generally recognized. The operation of the partnership between geologist and geophysicist is relatively straightforward in reflection seismograph exploration as the geophysical maps are similar to those with which geologists are familiar. In geophysical methods based on potential fields (gravity and magnetic) the relations to geology are not so direct and the possible ambiguities are much greater. Close cooperation of geophysicist and geologist in the evaluation of such surveys should produce particularly fruitful results. Some specific examples of both regional and local nature are illustrated and discussed.