Samples of Gdov (Estonia) and Volga (Russia) oil shales were oxidized by alkaline permanganate to study the distribution of carbon and the composition of the resulting oxidation products. Gdov shale was rather stable to oxidation and, after 42 hours 61.2 percent of the organic material remained unoxidized. Five hundred hours were required for complete oxidation, and the oxidation products consisted of CO/sub 2/, acetic, oxalic, and succinic acids. The oxidation products from Volga shale consisted of CO/sub 2/, acetic, oxalic, succinic, adipic, phthalic, benzenetricarboxylic, benzenetetracarboxylic, and benzenepentacarboxylic acids. The results indicated that Gdov shale is free of humic substances and is of sapropelic origin, while Volga shale is of sapropelic-humic origin.