Sir: Like other oil shales of the world, those of the Green River formation present difficult analytical problems. However, determination of the organic elementary compositions is essential to studies intended to increase the usefulness of oil shales. To obtain accurate values for the elemental composition of the organic materials in oil shale, complex corrections for the interfering effects of the mineral components are required on direct analysis of shale. The procedure presented here substantially reduces these interference problems by concentrating the organic matter. Although the organic and mineral components were not completely separated, the procedure concentrates oil-shale organic matter almost nonselectively in quantities sufficient for extensive study of its properties.