The Baltic region is of interest to organic geochemists because of the occurrence of crude oil accumulations, natural bitumen shows and oil shale deposits. For elucidating possible correlation between them, a suite of four crude oils, eight natural bitumens and three kerogeneous rocks was examined for organic carbon isotope composition. delta(13) C values for the studied crude oils and natural bitumens are similar and on an average -30.0 parts per thousand inherent in the Cambrian organic matter. In the series: oil --> maltha --> asphalt asphaltite the value of delta(13) C increases gradually showing the genetical relationship between the members of the series. No correlation by the carbon isotope composition between crude oils and natural bitumens, and organic matter of any studied kerogeneous rock is observed.