Resin and asphaltene fractions of crude oil from the Usa field (Timan-Pechora oil-and-gas province, Russia) obtained by fractional precipitation of asphaltenes and chromatographic separation of resins have been analyzed using Rock-Eval pyrolysis and flash pyrolysis (650A degrees C, 20 s) with on-line chromatographic/mass spectral detection of volatile products. It has been shown that the samples under study contain organic compounds with a relatively low molecular mass in an amount of 2.3 to 15.3 wt % as either impurities or moieties bound in resin and asphaltene molecules by labile chemical bonds. The products of flash pyrolysis of the samples under study differ in the relative amount of the "unresolvable complex mixture" of unidentified compounds; the chemical group and molecular composition; and the relative amount of identified types of compounds, such as normal and isoprenoid alkanes, alpha-olefins, cyclohexanes, cheilanthanes and hopanes, hopenes, pregnanes and steranes, alkylbenzenes, naphthalenes, phenanthrenes and anthracenes, and benzo- and dibenzothiophenes.