The primary objective of the Phase I ERDA High-Temperature Turbine Technology (HTTT) Program was to provide a ''Program and System Definition'' of the three-phase program which would culminate in the testing of a Technology Readiness Vehicle (TRV) at the end of a six-year period. The TRV is designed for use in a combined cycle using coal-derived fuels at a firing temperature of 2600°F; growth capability to 3000°F is projected. The Phase I results reported are based on a 2600°F gas turbine burning coal-derived fuels. The following major areas are covered: overall plant design descriptions; systems design descriptions; turbine subsystem design; combustor design; phase II proposed program; and phase III proposed program. Details regarding final results of each of these areas are presented. It is concluded that the water-cooled gas turbine in combined cycle has been shown to be capable of extremely attractive levels of performance, both in terms of efficiency and specific output. Coupled with the ability to tolerate a wide range of coal-derived fuels with minimum fuel treatment, an extremely attractive system is presented for the generation of electric power. Future technology development of the high-firing-temperature water-cooled gas turbine is expected to result in the commercial introduction of this concept in combined cycles by the late 1980's or early 1990's.