Next to coal, oil shale is our largest domestic fossil fuel resource. Commercial development will lead to environmental impacts which must be controlled if oil shale is to be developed in an environmentally sound manner. Shale oil can be produced by three methods: mining and surface retorting, modified in situ, and true in situ. All require the application of heat to the oil shale. Studies of the baseline environmental conditions of the nature and source of emissions, effluents, and solid wastes from oil shale operations identified the following potential environmental impacts: (1) air quality, (2) water quality and hydrology, (3) solid waste disposal, and (4) surface subsidence. Under the Bureau of Mines mining environmental research--oil shale program, research is conducted in hydrology, rock mechanics, dust explosion and fire hazards, waste disposal, and water management. An environmental research facility is under construction in the oil shale deposits of northwestern Colorado where hydrologic, geotechnical, and environmental data will be obtained for designing environmentally safe mining methods.