Cytochrome P-450(CYP) enzymes are important in catalyzing the hiotransffrmation on manyendogeneous compounds and xenobiotics, including drugs and carcinogens. In the presentstudy, effect of nifedipine a voltage dependent calcium channel blocker on the induction ofCYP1A1 and 2B1 was investigated. Change of CYP1A1 and 2B1 activities were measuredby using specific enzyme activities and Western blot analysis. CYP1A1, as quantified by ethoxyresorufin-0-deethylase activity and Western blot with monoclonal antibody 1-7-1, increasedin liver microsome of nifedipine-treated spontaneous hypertensive rat(SHR. 30mg/kg.b.w, twicea day for 3days) but not in kidney microsome. CYP2B1, as quantified by benzyloxyresorufin-O-dealkylase activity and Western blot wit]1 monoclonal antibody 2-66-3, markedly increasedin liver microsome of nifedipine-treated SHR but slightly in kidney microsome. The resultsdemonstrate that nifedipine is a potent inducer of CYP2B1 in SHR.