The treatment of landfill leachate by Fenton process was carried out in a continuous stirred tank reactor (CSTR). The effect of operating conditions such as reaction time, hydraulic retention time, pH, H2O2 to Fe(II) molar ratio, Fenton's reagent dosage, initial COD strength, and temperature on the efficacy of Fenton process was investigated. It is demonstrated that Fenton's reagent can effectively degrade leachate organics. Fenton process reached the steady state after three times of hydraulic retention. The oxidation of organic materials in the leachate was pH dependent and the optimal pH was 2.5. The favorable H2O2 to Fe(II) molar ratio was 3, and organic removal increased as dosage increased at the favorable H2O2 to Fe(II) molar ratio. Temperature gave a positive effect on organic removal. (c) 2005 Elsevier B.V. All rights reserved.