Results are presented from research and development carried out by the Bureau of Mines on the gas-combustion oil-shale retorting process. Effects of the process variables, results of gas and shale distribution studies, tests on shale particle size, and other details of experimental programs are discussed. Various auxiliary information and problems associated with the retorting process also are included. Tabulations of the retorting test data and detailed oil recovery flow diagrams for the 6-, 25-, and 150-ton/day retorts, and drawings relating to retorting equipment are given.