A kinetic investigation into the photo-degradation of aqueous diethyl phthalate by Fenton reagent was conducted in this study. The obtained results showed the enhancement of diethyl phthalate (DEP) decomposition by UV irradiation with the Fenton reaction. It was found that H2O2 concentration, Fe2+ concentration, and aqueous pH value were the three main factors that could significantly influence the degradation rates of DEP. The highest degradation percentage (75.8%) of DEP was observed within 120 min at pH 3 in the UV/H2O2/Fe2+ system, with original H2O2 and Fe2+ concentrations of 5.00 x 10(-4) and 1.67 x 10(-4) mol L-1, respectively. The present study provides an effective approach to the treatment of wastewater containing DER (c) 2005 Elsevier B.V All rights reserved.