This handbook is primarily a description of the methodology of using earth resistivity techniques for locating cavities. Only a small portion of the handbook will be devoted to the theoretical considerations behind these techniques. However, the annotated bibliography cites ample literature to satisfy the needs of the theoretician. Along with earth resistivity techniques, several geophysical techniques will be examined in lesser detail with respect to cavity location. Micro-gravity, high-resolution seismic reflection profiling, and ground probing radar were selected because they show good success rates in cavity detection. High-resolution seismic profiling shows particularly good promise as an effective tool in cavity location. Techniques in photo interpretation will also be discussed with regard to possible cavity location.