The design of a high-temperature, high-work radial turbine for advanced small gas turbine engines is described. This turbine is designed to produce nearly 220 Btu/lb gas flow at 87.5% efficiency, with a 5:1 stage pressure ratio. Turbine inlet gas conditions are 17.5 atm and 2300°F. The resulting turbine configuration includes an air-cooled, 12-bladed rotor designed for 67,000 rpm, and a 20-vaned, air-cooled nozzle section of a reflex (supersonic) design. Both parts are IN 100 (PWA 658) investment castings. The discussion includes results of aerodynamic, structural, and thermal analyses. Also discussed is a fabrication study, which indicated that a casting development effort would be required to produce adequate material properties. This effort is currently underway, and consists of both an integral centrifugal casting approach and a bicasting technique. The test rig to be used for the turbine tests is described.