Six oil shales from different locations; the Green River formation of Colorado and Utah, the Antrim Basin of Michigan, and Morocco; having different Fischer "Assay oil yields were retorted using three retorting atmospheres; N2 , N2/steam, and N2/steam/02; using the same retorting conditions. The products (oils, gases, waters, and shales) were analyzed and the data are reported. Changing retorting atmospheres had little observable effect on the product oils; however, there was a great deal of change in the composition and amount of gas produced. Steam in the retorting atmosphere increased the amount of carbon dioxide produced and decreased the amount of carbonate and organic carbon in the retorted shale. Addition of oxygen to N2/steam and increasing the maximum temperature compounded the above effect.