A high-performance liquid chromatographic method was developed to determine nifedipine in biological fluids, by using ultraviolet detection at 240 nm.Phenacetin was chosen as internal standard.A Nova-Pak C18(4 um, 3.9?150mm) was employed with methanol-water (68:32) as mobile phase. Nifedipine was extracted by ethyl acetate with a percentage of recovery about 95.3?1.0%. The limit of detection of this method for nifedipine was 4 ng for an injection volume of 20 ul. One major metabolite was formed from nifedipine after incubation with human liver microsom-es, the NADPH generating system was needed in this metabolic ptocess. Km and Vmax measured by nifedipine disappearance from roicrosomal incubation mixture were 58.0 umol/L and 1.51 nmol/mg/min, respectively