Abstract: Naftopidil(Naf), a novel antihypertensive drug, was determined by HPLC-UV method. The plasma concentration and pharmacokinetics of naftopidil have been investigated in rats after single oral doses of 10, 20 and 30 mg·kg^-1. The drug was found to conform to a twocompartment model. Tp was in the range of 0.42 h to 0,90 h. T_1/2β was 7.08 h after the 10 mg·kg^-1 dose, 4.78 h after the 20 mg·kg^-1 dose and 5.83 h after the 30 mg·kg^-1 dose. The Cmax, AUC and CL/F appeared to be dose dependent at the doses not higher than 20 mg·kg^-1. Naf was found in many tissues after a single oral dose of 20 mg·kg^-1. The top level tissues were intestine, liver and lung at 15 minutes after administration, while the uteroovarian tissue was the highest at 6 h. Naf can be extensively metabolized since the total excretion of the parent compound in urine and faeces was less than 1% of the dose. From 82% to 97% of Naf in plasma was shown to be bound to protein.