Response surface methodology was used to optimize the Fenton treatment of amoxicillin and cloxacillin antibiotic aqueous solution. Under optimum operating conditions (hydrogen peroxide (H2O2)/chemical oxygen demand (COD) molar ratio 2, H2O2/Fe2+ molar ratio 76, and reaction time 90 min at pH 3), 78.98, 72.96, and 81.18 removal of COD, total organic carbon, and ammonia-nitrogen, respectively were achieved. Experimental removal efficiency and model prediction were in close agreement (<0.4 error). Fourier transform infrared spectra indicated degradation of the beta-lactam bond of the antibiotics. Biodegradability (BOD5/COD ratio) improved from zero to 0.33, indicating that Fenton treated antibiotic aqueous solution was amenable to biological treatment. © 2013 Balaban Desalination Publications. All rights reserved.