Geophysical prospecting for petroleum strictly is an indirect method of mapping geologic structure. In it, three successive steps can be recognized in all of the methods: (1) the mapping of the areal variation of some physical effect at the surface; (2) the determination of the subsurface distribution of some physical property producing the surface effect; and (3) the interpretation of the geologic situation corresponding with the distribution of that physical property. The methods have their limitations through the incomplete concordance between structure and the distribution of those physical properties, lack of knowledge of the geophysical constants of formations, inexperience, and erroneous geologic information. There is a bare possibility of the direct determination f the presence of petroleum by the electric method. Although the positive value of geophysical methods has been demonstrated, they are no panacea for all the difficulties in prospecting for oil.