The Lawrence Berkeley Laboratory (LBL) under the auspices of the U. S. Energy Research and Development Administration (ERDA) has embarked on a cooperative project with the Comisi6n Federal de Electricidad of Mexico (CFE) in a detailed study of the producing geothermal reservoir at Cerro Prieto, Baja California (Figure 1). Presently, 75 megawatts of electrical power are produced at Cerro Prieto; CFE plans to expand the capacity several fold over the next decade. The cooperative project incorporates studies of the geologic, hydrogeologic, geochemical and geophysical settings of the Cerro Prieto Field, as well as its reservoir engineering and subsidence characteristics