Nevirapine is a non-nucleoside reverse transcriptase inhibitor for the treatment of HIV-1-infected patients. A simple and rapid high-performance liquid chromatographic method for the quantification of nevirapine in human plasma is described. Sample pretreatment consists of protein precipitation with acetonitrile. The analyte is separated from endogenous compounds by isocratic reversed-phase, ion-pair, high-performance liquid chromatography with ultraviolet detection at 282 nm. The method has been validated over the range of 52-10400 ng/ml using 250 microl of plasma. The assay was linear over this concentration range. Within- and between-day precisions were less than 4.5% for all quality control samples. The lower limit of quantitation was 52 ng/ml. Recovery of nevirapine from human plasma was 94.5%. This validated assay is suited for use in pharmacokinetic studies with nevirapine and can readily be used in a hospital laboratory for the monitoring of nevirapine concentrations.