The paper investigates the trend of clean coal technology research and development in the U.S. through the 21st Biennial Conference on Carbon. The subjects investigated are an outline of the Clean Coal Technology Demonstration Program of U.S. Department of Energy, the developmental trend of integrated gasification combined cycle power generation (IGCC), the trend survey of the ENCOL mild gasification project, and coal-related research surveys in the 21st Biennial Conference on Carbon. In CCT program, the following are now worked on: 11 projects on coal-fired power generation systems; 20 on pollution control devices; 5 on coal processing; 5 on industrial application. Further, five IGCC demonstrative projects are being carried out. Three power plants are run by the combustion by advanced air-blown type gasification technology, and at four power plants a demonstrative operation is conducted of the subsystem for energy saving and high temperature gas cleaning. In the ENCOAL process, low-sulfur coal is heated, and process-derived fuel and coal-derived liquid are produced from it by using thermal cracking and mild gasification technology, LFC (liquids from coal technology). 167 refs., 86 figs., 55 tabs.