The pharmacokinetics of nifedipine was studied after oral coadministration of nifedipine (5 mg/kg) with quercetin (1.5, 7.5, 15 and 30 mg/kg, respectively) and 0.5 h or 3days pretreatment with quercetin (1.5 and 7.5mg/kg) in rabbits. Pretreatment of quercetin significantly (p<0.05, at 0.5 h; p<0.01, at 3 days) increased the plasma concentration of nifedipine, but not significant in coadministraiton. The area under the plasma concentration-time curve (AUC) and the peak concentration $(C_{max})$ of nifedipine pretreated with quercetin were increased significantly (p<0.05, at 0.5 h; p<0.01, at 3 days) compared to the control. By coadministration of quercetin, only 7.5 mg/kg of quercetin increased plasma AUC and $C_{max}$ of nifedipine significantly (p<0.05) compared to the control. Plasma AUC of intravenous nifedipine (1 mg/kg) is $4235;{pm};1192;ng/ml{cdot}hr$. Pretreatment of quercetin significantly (p<0.05, at 0.5 h; p<0.01, at 3 days) increased the absolute bioavailability (AB%) of nifedipine to 23.9-29.2% compared to the control (17.8%). Coadministration of quercetin showed no significant effect on the AB% of nifedipine except for 7.5 mg/kg. It is suggested that quercetin alters disposition of nifedipine by inhibition of P-glycoprotein efflux pump and its first-pass metabolism. The dosage of nifedipine should be adjusted when it is administered chronically with quercetin in a clinical situation.