Shale oil, produced at Rifle, Colorado, by the U.S. Bureau of Mines through NTU retorting of oil shale, has been studied. These investigations included (1) the development of techniques for analysis of shale oil, (2) the determination of the composition of shale oil, (3) the examination of the tar bases and tar acids of shale oil, and (4) the investigation of the stability of shale oil.