In order to understand the mechanism of the regulation of drug metabolizing enzyme gene expression, we have studied the induction of CYP1A1 and GST$alpha$, $mu$, $pi$ enzymes in Japanese monkey and rhesus monkey after the treatment with 3-methylcholanthrene (3MC) and di-n- butyl phthalate (DBP) and bisphenol A (BPA). The levels of mRNA were measured by RT-PCR in brain, intestine and liver. In the case of adult monkey, treatment with 3MC induced CYP1A1 mRNA in liver by 10-fold. The treatment with DBP induced CYP1A1 mRNA. Effects of 3MC and DBP on GST mRNA expression was not clear. But GST$mu$ was slightly inhibited by the treatment with 3MC and DBP. GST$pi$ was not induced by the treatment with 3MC and DBP in liver. GST$alpha$ was slightly induced by the treatment with 3MC and DBP in liver. In the case of fetus monkey, the basal levels of fetus CYP1A1 mRNA and GSTs mRNA were relatively low compared to adult monkey. As the age of monkey increased, the basal levels of CYP1A1 mRNA were also increased. 3MC induced the expression of CYP1A1 mRNA in liver. The levels of GST$mu$ and GST$alpha$ were not changed by the treatment with 3MC and DBP. GST$pi$ was slightly induced by the treatment with 3MC and DBP.