Puerarin, the main isoflavone glycoside found in the root of Pueraria lobata, has been used for various medicinal purposes in traditional Chinese medicine for thousands of years. The purpose of this study was to investigate the protective effects of puerarin against hepatotqxicity induced by carbon tetrachloride ($CCI_4$) and the mechanism of its hepatoprotective effect. In mice, pretreatment with puerarin prior to the administration of $CCI_4$ significantly prevented the increased serum enzymatic activity of alanine aspartate aminotransferase and hepatic malondialdehyde formation in a dose-dependent manner. In addition, pretreatment with puerarin significantly prevented both the depletion of reduced glutathione (GSH) content and the decrease in glutathione S-transferase (GST) activity in the liver of $CCI_4$-intoxicated mice. Hepatic GSH levels and GST activity were increased by treatment with puerarin alone. $CCI_4$-induced hepatotoxicity was also prevented, as indicated by liver histopathology. The effects of puerarin on cytochrome P450 (CYP) 2E1, the major isozyme involved in $CCI_4$ bioactivation, were also investigated. Treatment of the mice with puerarin resulted in a significant decrease in the CYP2E1-dependent aniline hydroxylation in a dose-dependent manner. Consistent with these observations, the CYP2E1 protein levels were also lowered. Puerarin exhibited anti-oxidant effects on $FeCl_2$-ascorbate induced lipid peroxidation in mouse liver homogenates, and on superoxide radical scavenging activity. These results suggest that the protective effects of puerarin against the $CCI_4$-induced hepatotoxicity possibly involve mechanisms related to its ability to block CYP-mediated $CCI_4$ bioactivation, induction of GST activity and free radical scavenging effects.