In the present study, the effects of allopurinol on paraquat toxicity were investigated in paraquat-treated rats. The surivals of paraquat-treated rats were increased by allopurinol treatment. The contents of glutathione in liver and kidney were significantly decreased by paraquat, but restored by allopurinol. The activity of xanthine oxidase was significantly reduced but NADH dehydrogenase was not changed by allopurinol teatment. The activities of catalase, SOD and glutathione peroxidase in liver were significantly decreased by paraquat but catalase was restored by allopurinol treatment.