The metabolism of 9-methylanthracene by liver microsomal preparations from 3-methylcholanthrene-treated rats was examined. The principal metabolites identified were 9-hydroxymethylanthracene, the 1,2- and 3,4-dihydrodiols of the parent hydrocarbon and the 3,4-dihydrodiol of the 9-hydroxymethyl derivative. A small amount of a product that appeared to be a phenolic derivative of the hydrocarbon was also formed. The structures of the major metabolites were confirmed by u.v., n.m.r., and mass-spectral analysis and, wherever possible, by direct comparison of their chromatographic properties with those of the authentic compounds. 9-Hydroxymethylanthracene was further metabolized by rat-liver microsomal preparations to the 3,4-dihydrodiol but not to the related 1,2-dihydrodiol.