The authors extend the analysis of hybrid fossil-geothermal power plants to compound systems which combine the features of the two previously analyzed hybrid plants, the geothermal preheat and the fossil superheat systems. Compound systems of the one- and two-stage type are considered. A summary of formulas to assess the performance of the plants is included. From the viewpoint of thermodynamics, compound hybrid plants are superior to individual all-geothermal and all-fossil plants, and have certain advantages over basic geothermal-preheat and fossil-superheat hybrid plants. The flexibility of compound hybrid systems is illustrated by showing how such plants might be used at several geothermal sites in the western United States. 26 refs.