The identification of seven polyaromatic ring systems in petroleum is reported. The ring systems are 1.12,2.3-dibenzoperylene; 1,12-o-phenyleneperylene, pyreno(1.3:10'.2')pyrene; 2.3,10.11-dibenzoperylene; 1,2,4,5-dibenzopyrene, benzo(e)pyrene, and benzo(g)chrysene. These polyaromatic hydrocarbons were isolated by a separation scheme involving ion exchange chromatography, gel permeation chromatography, and thin-layer chromatography and were identified by fluorescence spectroscopy. Gel permeation chromatogaphy separated pericondensed aromatic ring systems from catacondensed ring systems and the other components of an acid concentrate.