The next generation of large, heavy-duty, single-shaft gas turbines, 501G, with a turbine inlet temperature in the 1500 degrees centigrade range has been developed by Mitsubishi Heavy Industries, Ltd (MHI). Many advanced component technologies (a high efficiency compressor, a steam cooled combustor, a high temperature turbines, etc.) are employed in this turbine and achieve an excellent combined cycle performance. Various component tests have been conducted over the past 3 years. From February, 1997, a trial operation of the 501G for 60 Hz utilities was performed at the verification test combined cycle plant at MHI. Takasago plant in Japan to verify its high performance, reliability and maintainability. Also, during the trial operation at this plant, more than 1800 instrumentation systems were installed in the engine. The flow path characteristics, metal temperatures, pressures, strains, sound pressure levels, exhaust emissions, etc. were measured over the full range of operating conditions. All important characteristics, including the cooling characteristics, and components reliability were verified.