There are reported gas chromatography, gas chromatography/mass spectrometry and carbon isotopic data on the oils sampled in caldera of the Uzon volcano (East Kamchatka). The Uzon volcano is located in the west of the eastern Kamchatka basin which is made up of thick Paleogene-Neogene sedimentary rocks. Its caldera is made up of lacustrine volcanogenic-sedimentary formations of Pleistocene age (38–70 thousand years), lying on dense basalts. Two samples studied were heavy oils (0.915 g/ml) and contained 2 sulfur; 2.5 paraffin, 9.3 waxes; 1.4 wt olefinic hydrocarbons. Their gas chromatograms show a mono-modal distribution for n-alkanes with a maximum at C18. Pristane/Phytane concentration ratios were measured to be 0.48–0.52. Olefinic hydrocarbons were interpreted to be of hydrothermal origin. Sterane and triterpane biomarkers indicated a low maturation degree and a lacustrine orgin of the initial organic matter. The Uzon oil was found to be isotopically heavy with a δ13C value of −21‰14C isotope was detected, which indicates that recent plant organic matter was significantly involved in oil generation process.