High-efficiency waste-to-energy plants are required to achieve energy savings and protect the environment. A high-efficiency pilot plant providing stable 500°C/100ata steam started a demonstration run from February 1998 by NEDO, and has operated satisfactorily for about one year. A stoker combustion furnace, highly corrosion-resistant coating and superheater tubing were developed and applied to ensure high-performance pollution control and long-term durability for the high-temperature and high-pressure boiler. Its excellent performance was clarified by the demonstration run.