Feeding diets containing cauliflower to rats inhibited hepatic residues of polybrominated biphenyls (PBB) with a reduction of fatty livers produced by 50 ppm of dietary PBB. Cauliflower diets also reduced the toxic effects of aflatoxin in Fischer rats, i.e. prevented mortality and internal hemorrhaging, and reduced liver pathology. These diets enhanced hepatic aminopyrine N-demethylase and p-nitroanisole O-demethylase activities. A kinetic study of aryl hydrocarbon hydroxylase reaction rates showed that apparent Km was lower in liver, kidney, and intestine, with a higher Vmax in the intestine. These data, combined with earlier studies, suggest that microsomal enzyme induction, especially in liver and intestine, affords a detoxication mechanism of two widespread food contaminants when animals are under a cauliflower dietary regimen.