Sandia National Laboratories has been developing surface geophysical techniques to map in situ processes, in particular the underground coal gasification process. The potential use will be discused of the controlled source audio-frequency magnetotelluric electromagnetic surface geophysical technique to map and monitor the UCG process. The technique has been field tested for the UCG application by mapping coal mine fires and by mapping the Hanna II, Phases 2 and 3 and Rawline T-2 cavities. Results of these field trials demonstrate that the CSAMT technique is an excellent technique for the determining the lateral extent of the UCG process. In addition, the shape of the process is readily apparent in the "raw" data without extensive data reduction, and by careful design of the mapping survey; the results are not degraded by the presence of the surface plumbing. A brief description will be fiven of the deployment of the CSAMT for UCG process mapping and monitoring.