Chemical oxidation for the partial oxidation of nonbiodegradable compounds has been used to enhance biotreatment. In this study, Fenton's reagent was used in batch mode to enhance the biological treatability of the leachate from an improperly managed municipal solid waste landfill. Removal of color by the oxidation process was also investigated. For this particular landfill leachate, the optimum H2O2 dose was found to be 1500 mg/L with the molar ratio of Fe2+/H202 being 0.08. Decolorization efficiency as high as 92.0% was achieved. For the removals of both organics and color in the leachate, the effective pH was in the vicinity of 3.5. Chemical sludge production increased with increasing Fe2+ dose at a fixed H2O2 dose. The ratio of BOD20/COD increased after the oxidation, which indicated that the Fenton oxidation could be effective prior to the biological process.