Metabolism of cannabichromene (CBC) was studied in hepatic microsomal incubates from mouse, rat, rabbit, guinea pig, cat, hamster, and gerbil. Metabolites were extracted with ethyl acetate, concentrated by chromatography on Sephadex LH-20, and identified by GC/MS as trimethylsilyl derivatives of both the metabolites themselves and their hydrogenated analogues. Thirteen metabolites were identified. The major metabolites were monohydroxy compounds with hydroxylation at all positions of the pentyl and methylpentenyl chains. An epoxide and its derived dihydrodiol were formed from the double bond in the methylpentenyl chains. Several unidentified decomposition products were found in the extracts from mouse, gerbil, and cat; these appeared to have been produced by the opening of the dihydropyran ring. Metabolism varied considerably between the species, although the trans-hydroxy metabolite 5'-hydroxy-CBC was the major metabolite in most cases. Metabolites hydroxylated in the pentyl chain were more abundant in mouse, rabbit, and cat; the hamster, gerbil, and cat produced the most epoxide-derived material.