A simple and reproducible method for the simultaneous determination of the antimicrobial agent pefloxacin and the anti-inflammatory drug fenbufen with its metabolite felbinac in human plasma is described. It involves a two steps liquid-liquid extraction and separation using an Adsorbosphere SAX column with ultraviolet detection at 280 nm. 2-[4-(2′-furoyl)phenyl]propionic acid is used as internal standard. The coefficients of variation are less than 5%. The lower limits of detection are 0.1, 0.3 and 0.1 μg/mL for pefloxacin, fenbufen and felbinac, respectively. This method was found to be applicable to pharmacokinetic and pharmacodynamic studies of each drug after the concomitant administration of pefloxacin and fenbufen.