A high-performance liquid chromatographic method was developed for the determination of a new phospholipase A 2 inhibitor, NQ12, in human plasma and urine. The sample preparation was simple: 2 volumes of acetonitrile were added to the biological samples to deproteinize it. A 50-μl aliquot of the supernatant was injected onto a C 18 reversed-phase column. The mobile phase employed was 0.05M acetate buffer (pH 3): acetonitrile: methanol (30:45:25, v/v/v) and run at a flow rate of 1.5 ml/min. The column effluent was monitored by a UV detector set at 298 nm. The retention times for NQ12 and the internal standard were approximately 5.5 and 7.0 min, respectively. The detection limits for NQ12 in human plasma and urine were all 20 ng/ml. The coefficients of variation of the assay (within-day and between-day) were generally low (below 11.8%) for human plasma and urine. No interferences from endogenous substances were found.