Chromate-mass spectrometry with a computerized data processing system has been used to study the qualitative and quantitative composition of sterane (C-21-C-29) and terpane (C-19-C-35) hydrocarbons - biomarkers - in crude oils from the Volga-Urals oil- and gas-bearing province. Conclusions have been drawn concerning the geochemical types and the conditions of formation of the Volga-Urals crude oils. It has been shown that the oils studied can be divided into two very different types with respect to the geological and geochemical conditions of their generation - Proterozoic and Paleozoic. Oils of the two types were generated by marine organic matter and differ in the composition of the hopane and sterane biomarkers. Crude oils of the Proterozoic type were generated in carbonate deposits and have moderate catagenetic maturity. The Paleozoic crude oils (Devonian-Carboniferous) were generated in clay deposits and are noted for a higher degree of maturity.