The carbon tetrachloride(CCl₄) has been demonstrated to have a hepatotoxic effect in human or many other species. To investigate the enzyme induction of mixed function oxygenases in liver of male Sprague-Dawley rats a single 0.1, 0.5 ml/kg dose of carbon tetrachloride were given. At 24 hr after a single dose of 0.1 ml CCl₄/kg weight, methanol extract of Hedera rhombea leaves was administered with 100, 500 mg/kg weight. Assays of 7-ethoxyresorufin-0-deethylation(EROD), 7-benzyloxyresorufin-0-dealkylation(BROD), 4-nitrophenol-UDP-glucuronosyltransferase(UDPGT), Western blot and RNA slot blot were used as representatives of the activities of cytochrome P-450 enzymes. The change of the activity of CYP1A1 form measured by EROD assay and Western analysis using 1-7-1 monoclonal antibody was not observed. The activity CYP2B1 form by BROD assay and using 2-66-3 monoclonal antibody was remarkably increased. Elevated level of CYP2B1 mRNA was shown by slot hybridization with 2B1-specific probe. Administration of methanol extract of Hedera rhombea leaves reversed the enzyme activity and the level of mRNA, which suggest the chemoprotective effect of methanol extracts of Hedera rhombea leaves to carbon tetrachloride hepatotoxicity.