Benzo[a]pyrene (BaP) is known to induce tumors in lung, forestomach, and skin in experimental animals. Earlier studies have suggested that glutathione S-transferase n (GST pi) is involved in the detoxification of the “ultimate” carcinogenic metabolite of BaP, 7p, 8a-dihydroxy-9a, IO(x-oxy-7tBt9tIO-tetrahydrobenzo[a]pyrene (BPDE). The constitutive expression of GST pi in the liver of the male CD-1 mouse is higher than that of the female, and BHA has been shown to preferentially induce GST pi in the female as compared with the male mouse. The present studies were therefore designed to compare the susceptibility of male and female CD-I mice to the carcinogenic effects of BaP and the protective effect of BHA. Results of these studies show that the female CD-1 mice are more susceptibile to the carcinogenic effect of BaP than the males and that the attenuation of BaP-induced carcinogenesis by BHA appears to be restricted only to the females.