A simple HPLC method has been developed for the determination of ticlopidine in human plasma. Plasma samples were buffered at pH 9 and extracted with n-heptane-isoamyl alcohol (98.5:1.5, v/v). Imipramine was used as internal standard. Chromatography was performed isocratically with acetonitrile-methanol-0.05 M KH2PO4 (20:25:55, v/v) at pH 3.0 containing 3% triethylamine at a flow-rate of 1 ml/min. A reversed-phase column, Supelcosil LC-8-DB, 15 cm x 4.6 mm I.D., 5 microns particle size, was used. The effluent was monitored by UV absorbance detection at 235 nm. The method showed good accuracy, precision and linearity in the concentration range 5-1200 ng/ml. The limit of quantitation was 5 ng/ml, with a precision (C.V.) of 8.91%, which is the same as that achieved by other authors with a previously published GC-MS method. The procedure described in this paper is simple and allows the routine assessment of ticlopidine plasma concentration in pharmacokinetic studies following therapeutic doses in human subjects.