A comparative analysis has been made of the physicochemical properties and structural-group composition of acids isolated from crude oils of the Anastasievsko-Troitskoe (Krasnodar krai, Russia) and Naftalan (Azerbaijan) oil fields. For each crude, the following three fractions of acids have been obtained by vacuum fractionation and analyzed: 240-350, 350-390, and >390; their elemental composition has been determined; and formulas for average acid molecules in each of the fractions have been derived. It has been shown that the acids of the 240-350 degrees C fraction are monocyclic monocarboxylic acids with the five-membered naphthene ring. The fractions with the higher boiling points contain bicyclic naphthenic acids and, possibly, hydroxy acids. The acid fractions obtained from the Anastasievsko-Troitskoe oil are distinguished by the presence of aromatic structures and a significant amount of unsaponifiable components, especially in the 240-350 degrees C fraction, which is of the greatest practical interest.