In this study, two cephalosporin groups of antibiotics (cefepime and cefixime) and their combinations with clavulanic acid, beta lactamase inhibitor, were simultaneously analyzed by HPLC method. The optimum separation was carried out on MZ C-18 column (250 x 4.6 mm; i.d. 5 mu m) with mobile phase consisting of an acetonitrile - 0.01% phosphoric acid (pH 2.5) (15 : 85, v/v) binary mixture. Detection was performed using a diode array detector at 228 nm. Under these experimental conditions, the analysis was accomplished in about 10 min. The developed method is specific, linear, sensitive, accurate, precise, and robust. The method was completely validated showing satisfactory data for all the parameters tested. Finally, the proposed method was successfully applied to two combined pharmaceutical dosage forms containing cefepime with clavulanic acid and cefixime with clavulanic acid.