The purpose of this study was to investigate the effect of coadministration and 3 days-pretreatmemt of niledipine (2, 10 mg/kg) on the pharmacokinetic parameters and bioavailability of paclitaxel (50 mg/kg) after oral administration in rats. Coadministration of nifedipine with paclitaxel did alter the $C_{max}$ (115${pm}$29 ng/ml without nifedipine; 135${pm}$35 ng/ml with nifedipine (10 mg/kg): p<0.05) and AUC (188${pm}$459 ng/mlㆍhr with-out nifedipine; 2546${pm}$642 ng/mlㆍhr with nifedipine; p<0.05). Three days treatment of nifedipine on the prior to paclitaxel administration increased the $t_{1/2}$ 〔9.90${pm}$2.47 hr without nifedipine; 12.37${pm}$3.12 hr with nifedipine (2 mg/kg): 12.83${pm}$3.32 hr with nifedipine (10 mg/ml); p<0.05] and AUC [1833${pm}$459 ng/mlㆍhr without nifedipine; 2663${pm}$648 ng/mlㆍhr with nifedipine (2 mg/kg): 3006${pm}$734 ng/mlㆍhr with nifedipine (10 mg/ml): p <0.05]. Drug interaction between nifedipine and paclitaxel decreased the elimination rate constant and increased the oral bioavailability of paclitaxel. On the basis of the results of this study, it might be considered that nifedip ine may inhibit cytochrome P450, which are engaged in paclitaxel metabolism, result in increased $t_{1/2}$ and AUC of paclitaxel. However, further study should be conducted to clarify the roles of cytochrome P450 and P-glycoprotein on paclitaxel bio-availability wit/or without nifedipine.