Present study was investigated the hepatic effects of equol on the 7,12-dimethylbenz(a)anthracene (DMBA)-induced enzymatic activity and expression of CYP1A1 and CYP1B1 in mice. Equol was administered orally at 5 and 25 mg/kg BW for 4 weeks. Subsequently, mice pretreated with equol received DMBA intragastrically twice a week for 2 weeks. DMBA induced CYP1 activity as well as the expression of CYP1A1 and CYP1B1. Each of these effects was significantly reduced by equol in dose-dependent manner (p<0.05). Equol also reduced the relative AhR mRNA expression, similar to its effect on CYP1A1. These results suggest that equol modulates the CYP1A1 through a reduction of AhR expression in mice treated with DMBA.