Chromate-mass spectrometry with a computerized data processing system has been used to study the composition of C-21-C-29 sterane biomarkers and C-19-C-35 terpane biomarkers in tertiary crude oils of the North Sakhalin, Okhotsk-Kamchatka and Anadyrsk oil and gas basins. The composition of biomarkers of the crude oils studied indicates the existence in the given oil basins of two geochemical types: the first type of oil, of marine planktogenic origin, is found chiefly on Sakhalin, is generated in argillaceous-siliceous deposits and has a wide range of maturity - from immature to moderate maturity; the second type of crude oil (Sakhalin, Kamchatka, the Anadyrsk oil and gas basin) is genetically related to continental-type organic matter deposited in coastal-marine argillaceous-siliceous rock masses. Crude oils of this type have no more than moderate maturity. An intermediate type of crude oil, generated from organic matter of mixed genesis, is common on Sakhalin.