The NASA Lewis Research Center (LeRC) as Project Manager of the Department of Energy's Automotive Heat Engine Program, is developing advanced gas turbine and Sterling engines for automobiles. To accomplish the program goals of improved fuel economy, reduced emissions, and broad alternative fuel capability major development programs have been undertaken for both engines. These programs are described along with the predicted characteristics of the engines under development and the key technology problems that must be resolved to achieve these objectives. NASA LeRC is also responsible for the development of the power con-version systems for the Parabolic Dish Solar Thermal Power Systems being developed for the Department of Energy by the NASA Jet Propulsion Laboratory. The requirements of this solar thermal application are reviewed and compared with the predicted characteristics of the automobile engines under development. A good match was found in terms of power level and efficiency when the automobile engines, designed for maximum powers of 65-100 kW (87 to 133 hp) were operated to the nominal 20-40 kW electric output requirement of the solar thermal application. At these reduced power levels it appears that the automotive gas turbine and Stirling engines have the potential to deliver the 40* percent efficiency goal of the solar thermal program. However, in-depth studies are required to determine the extent of modifications required to adapt the engines for the solar application, and to fully assess the probable life, durability and resultant efficiency that can realistically be achieved in this application.