Acid catalysis of high-molecular-mass paraffin-cycloparaffin fractions (bp > 350 degrees C of oils of different genotypes was carried out. Despite the fact that C-10-C-13 adamantanes and C-14-C-16 diamantanes are absent from the > 350 degrees C fraction (these hydrocarbons boil in the range of 190-286 degrees C), they are regenerated during the catalysis. Moreover, as catalysis proceeds, the amount of polymethyl substituted adamantanes and diamantanes increases. The generation of adamantane hydrocarbons might be expected as a result of isomerization of tricyclic terpanes, namely, cheilanthanes. It is interesting that, unlike for 30-normethylhopane-C-29 adiantane-and C-31-C-35 homohopanes, an increase in the extent of catalysis led to a decrease in the relative amount of 17 alpha(H),21 beta(H)-hopane (C-30), but this was not due to its isomerization into thermodynamically more stable 17 alpha(H),21 beta(H)-diahopane. As regards regular C-27-C-29 steranes, an increase in the extent of catalysis decreased the relative amount of the lower homologues C-27 and C-28 relative to C-29 steranes. Among C-29 sterane epimers, the amount of the beta beta-epimers decreased in comparison with that of the alpha alpha-species.