Five crosshole-type seismic surveys, each employing the two commonly used seismic wave generation sources (explosive and mechanical), are studied to evaluate the reliability of each source technique to produce comparable seismic velocities. The study documents field procedures and equipment and discusses seismic wave identification and velocity analysis techniques. Comparison of the resulting velocities (compressional and shear) produced by the two different sources indicates that quite similar results can be obtained when proper field and interpretation procedures are used. General field considerations to be included in a crosshole survey using either source mechanism are discussed as a guide to producing high-quality seismic velocity results. These include the number of borings and their spacing and arrangement, test depth intervals, verticality measurements, hole coupling, orientation of sensors, and measurement of the instant of energy generation.