This is a status report from the development of a 150 kW (200 hp) Stirling prototype engine intended for medium duty automotive application. The basic concept and some of the components were developed on a small 40 kW (55 hp) experimental engine of V4 configuration. In the report emphasis is laid on the presentation of the development of specific Stirling engine components such as heat exchangers and control system. The present status of performance as well as the final objectives are given. The installation of the engine in a truck and projected truck performance in a typical driving cycle are presented and discussed.