A rapid and accurate assay for the determination of roxatidine, a selective H2-receptor blocker, in human plasma was developed. Analysis was performed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detector. Roxatidine acetate, a prodrug of roxatidine, is metabolized rapidly to roxatidine following oral administration. Roxatidine and the internal standard (ranitidine) were extracted from plasma by solid-phase extraction. The mobile phase of HPLC was consisted of 20 mM KH2PO4 (pH 7.0) and acetonitrile (5:1, v/v). The calibration curve for roxatidine was linear over the range of 5 to 1000 ng/mL. The precision and accuracy of within- and between-run were within 10% for roxatidine. The recovery of roxatidine was over 87% for both low and high concentrations (15 and 500 ng/mL) and the lower limit of quantitation (LLOQ) was 5 ng/mL. The method was successfully applied to a pilot pharmacokinetic study of roxatidine in healthy subjects.