The possible need within the near future for synthetic liquid fuels to augment the supply from petroleum in the U.S. has revived interest in oil shales as a source of such fuels. Both industrial and governmental organizations are doing research and development work and oil-shale processes. This report presents largely the results of research and development work that has been done by the U.S. Bureau of Mines since 1944. This work has been confined principally to studies of the Green River oil shales of the Rocky Mountain area of the U.S. The report includes the results of analyses showing the chemical and physical characteristics of the shales, the determination of the heat and other processing requirements for converting the organic matter in these shales to oil, the determination of the composition of shale oils produced by some different retorting processes, the effect of chemical composition on the refining characteristics of these oils, the results of laboratory, and bench-scale retorting and refining operations, and the determination of the quality of the fuels and secondary products as a measure of their suitability as petroleum substitutes.