The organic matter of oil shale samples from . four major Bulgarian deposits was investigated using thermal and oxidative treatments. Neutral oils from oil shales were obtained by low-temperature pyrolysis. Gas chromatography-mass spectrometry (GC-MS) was used to study the oxidation products and their chemical composition. A stepwise alkaline permanganate degradation of oil shale concentrate at ambient temperature was carried out, affording a high total yield (90 %) of oxidation products and a minimum yield of gas products. Two different types of high molecular substances were detected in oil shales. The results allowed conclusions to be made about the utilization of prospective Bulgarian oil shale deposits as energy sources.