A simple and reproducible method for the determination of roxithromycin in human plasma is presented. This method is based on liquid-liquid extraction with hexane-isoamylalcohol (98:2, v:v) and reversed-phase chromatography with spectrophotometric detection at 220 nm. The mobile phase consists of methanol-15 mM dihydrogen potassium phosphate (70:30, v:v), pH of the aqueous part of the mobile phase is 6.0. The column is operated at 60 degrees C. Clarithromycin is used as the internal standard. The limit of quantitation is 0.5 microg/ml and the calibration curve is linear up to 30 microg/ml. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy does not exceed 9%. The assay was used for pharmacokinetic studies.