1. Sulfur-containing and hydropurified fractions of aromatic hydrocarbon extracts from light catalytic cracking gas oil have been studied by a combination of gas chromatography and molecular spectroscopy. The total composition of the C10-C12 naphthalene hydrocarbons has been determined, and also the content of some derivatives of the benzothiophene and tetralin series. 2. The relative contents of individual dimethylnaphthalenes are close to the same values for all products studied.