Coso Geothermal Exploratory Hole No. 1 (CGEH No. 1) is the first deep exploratory hole drilled in the Coso Hot Springs area of Southeastern California. CGEH No. 1 was drilled to a depth of 4,845 ft in the central area of a large thermal anomaly and was a continuation of investigative work in that locale to determine the existence of a geothermal resource. The drilling and completion of CGEH No. 1 is described. Also included are the daily drilling reports, drill bit records, descriptions of the casing, cementing, logging and coring program, and the containment equipment used during the drilling operation