Kuhn and Winterstein reported the isolation of 2,6-dimethylnaphthalene from the products of pyrolysis of carotenoid pigments. The production of alkyl derivatives of phenanthrene and chrysene by the same type of cyclization can readily be formulated. The production of such hydrocarbons by the action of heat on naturally occurring substances, which include common constituents of foodstuffs would be of significance since such compounds might exhibit carcinogenic activity. Fractionation of the products of carotene pyrolysis confirmed the formation of 2,6-dimethylnaphthalene, but no more complex polynuclear aromatic hydrocarbons were isolated. The methods of analysis employed should have permitted the detection of such compounds in amounts considerably below 1%.