CYP1B1 enzyme metabolize PAHs and estradiol. CYP1B1 metabolize estradiol to 4-hydroxyestradiol that is considered as carcinogenic metabolite. Luciferase activity was induced about 20 folds over that control by 1 nM TCDD (2,3,7,8-tetrchlorodibenzo-p-dioxin) and these inductions were dose-dependent. Recent industrialized society, human hasbeen widely been exposed to widespread environmental contaminants such as PAHs (polycyclic aromatic hydrocarbon) that are originated from the incomplete combustion of hydrocarbons. PAHs are known to be ligands of the AhR (aryl hydrocarbon receptor). Induction of cytochrome P4501B1(CYP1B1) in cell culture is widely used as a biomarket for PAHs. Therefore we have studied the effect of PAHs in the human breast cancer cells MCF-7 to evaluate bioactivity of PAHs. Cytochrome P4501B1(CYP1B1) is known to be inducible by xenobiotic compounda such as policyclic aromatic hydrocarbon (PAH) and dioxins such as 2,3,7,8-tetrachloro-dibenzo-p-dioxin(TCDD). And these induction of CYP1B1 is also regulated by many categories of chemicals. In order to investigate the effects of several chemicals on CYP1B1 gene expression in luciferase gene, and then transfected into these cells. After treatment of chemicals, the luciferase activity was measured. We examined effects of PAHs on the CYP1B1-lucifrease reporter gene and CYP1B1 mRNA level. Benzo(k)fluoranthene showed strong response to CYP1B1 promoter activity stimulation, and also CYP1B1 mRNAs increase in MCF-7 cells in a concentration-dependent manner. flvonoids such as genistein decreased B(k)F induced luciferase activity at low concentration. it exhibited stimulatory effect at high concentration.