The dipole method of measuring resistivity is practical for use in studying the electrical properties of the earth’s crust. In such studies, electrical current is driven into the ground with a pair of electrodes spaced a few kilometers apart, and the electric field caused by this current is mapped to distances as great as 100 km. The principal advantage of the dipole method is the relatively small amount of cable which has to be laid out in comparison with that required by other electrode arrays. The results obtained from dipole surveys are very similar to the results obtained from other arrays, provided that the spacing factor is defined in an appropriate way, and that the earth is laterally homogeneous. If the electrical properties of the earth vary laterally, the dipole method provides results which differ widely from the data obtained with other arrays. This sensitivity to lateral effects is probably the most serious drawback to the use of dipole methods in crustal resistivity surveys.