Flavanone administered to female Fischer 344 rats at doses up to 1.00 mmol/kg/day for seven days did not induce ethylmorphine demethylation, aniline hydroxylation, hexobarbital oxidation or aldrin epoxidation. Flavanone administered at a dose of 0.05 mmol/kg/day for seven days increased glutathione-S-transferase activity with 1,2-dichloro-4-nitrobenzene and 1,2-epoxy-3-(p-nitrophenoxy)propane as substrates, and increased the glucuronidation of 1-naphthol and at 0.20 mmol/kg the glucuronidation of chloramphenicol. Flavanone administration did not alter sulfotransferase activity with 2-naphthol as the substrate, or enhance glutathione-S-transferase or glucuronyltransferase activity when added in vitro.