The modulatory effects of the Cyclamen trochopterantum tuber extract on hepatic drug-metabolizing enzymes, including aniline 4-hydroxylase (A4H; CYP2E1), ethoxyresorufin O-deethylase (EROD; CYP1A), methoxyresorufin O-demethylase (MROD; CYP1A), caffeine N-demethylase (C3ND; CYP1A2) aminopyrene N-demethylase (APND; CYP2C6), and erythromycin N-demethylase (ERND; CYP3A1), were examined in vivo in rats. The activities of all of these enzymes were induced by the cyclamen extract. In addition, Western-blot and RT-PCR results clearly showed that CYP2E1, CYP1A1/CYP1A2 and CYP2C6 protein and mRNA levels were substantially increased by four different doses of cyclamen. Although, the CYP3A1 protein level was increased significantly, the mRNA level was not changed. These results indicate that cyclamen tuber extract might have a potential not only to inhibit and/or induce the metabolism of certain co-administered drugs but also influence the development of toxicity and carcinogenesis due to the induction of the cytochrome P450-dependent drug-metabolizing enzymes.