This report is the first of a series dealing with the oil-shale reserves of the Green River formation in the Rocky Mountain Region. The known oil shale reserves of northwestern Colorado at present considered to have economic value apparently are confined to the Piceance Creek basin between the Colorado and White Rivers. The number of sampled sections is small, but there can belittle doubt that the Piceance Creek basin is a potential source of enormous quantities of liquid fuels and the related byproducts obtained from oil shale processing.