Abstract: In this study, we investigated pharmacokinetic of warfarin in sensitive and control patients by HPLC. The analysis performed by HPLC consisted of a column (Perfectsil Target, 5 μm, 125x4.0 mm) and an isocratic mobile phase of methanol: acetonitrile: phosphate buffer (pH: 3.5) (7:55:38, v/v), flow rate: 1 mL min-1 and UV detection at 270 nm. The assay was linear in warfarin concentration ranges of 0.1-10 μg mL-1 (r2 = 0.9975) and with Relative Standard Deviation (RSD) of <8% for inter-day and <6% for intra-day. The mean warfarin blood concentration of 54 patients was 1.2 ± 0.6 μg mL-1.