In the present study, protein oxidation (PCO content) and DNA-protein crosslinks (DPC coefficient) were investigated in the viscera of mice exposed to a municipal landfill leachate at various concentrations for 7 days. The study was designed to investigate the injuries and a possible mechanism of landfill leachateinduced toxicity on mammals. The results indicate that the leachate sample changed the ratio of viscera to body weight in all organs tested, and the effect on the brain was more obvious than that on other organs. The leachate ingestion increased PCO levels in the brain, kidney, liver and spleen in a concentrationdependent manner, but did not affect the content in the heart. Also, the leachate sample enhanced DPC formation in the tested organs in a concentration-dependent manner, and the responses of the liver, kidney and spleen were more sensitive than that of the brain and heart. These findings provide further evidence that landfill leachate-induced toxicity on mammals might involve the formation of free radicals, either via autoxidation or by enzyme-catalyzed oxidation of pollutants in leachate, and then attack of proteins and nucleic acids via generated free radicals.