A simple and sensitive high-performance liquid chromatographic method has been developed to measure megazol in human plasma. The method was optimized and validated according to the Washington Concensus Conference on the Validation of Analytical Methods (V.P. Shah et al., Eur. J. Drug Metab. Pharmacokinet., 15 (1991) 249). The criteria of complete validation were specificity, linearity, precision, analytical recovery, dilution and stability. It involved extraction of the plasma with dichloromethane, followed by reversed-phase high-performance liquid chromatography using a Kromasil(R) C-8 column and UV detection at 360 nm. The retention times of the internal standard (tinidazol) and megazol were 6.10 and 9.60 min, respectively. The standard curve was linear from 2 ng ml(-1) (limit of quantification) to 2000 ng ml(-1), The coefficients of variation for all the criteria of validation were less than 6%; 85 to 92% extraction efficiencies were obtained. Megazol was stable during the storage period (one month at -20 degrees C) in plasma and for two months at 25 degrees C in standard solution. The method was tested by measuring the plasma concentration following oral administration to rat and was shown to be suitable for pharmacokinetic studies.