Formal description of an earlier developed methodological approach to analysis of the hydrocarbon composition of petroleum and related materials is presented, which is based on C-13 NMR data and occupies an intermediate place between the currently accepted approach based on the information on the individual composition of hydrocarbon fractions and the traditional structural-group approach to the analysis of complex mixtures. Using particular examples, it was demonstrated that C-13 NMR spectroscopy of modem engineering design has sufficient sensitivity and resolving power (resolution) to unequivocally identify molecular fragments (including their stereochemistry) up to ten or more carbon atoms immediately in topped hydrocarbon fractions. Pie quantitative determination of corresponding groups of compounds with detection limit of the order of 0.1% is possible if a fraction sample of 50-100 mg is available, thus allowing the range of analyzable materials to be radically extended. It was shown that this approach makes it possible to tackle a number of long-standing petroleum geochemistry problems.