Free radicals may be involved in various pathogenesis processes. Tissue damage and cellular toxicity of some chemicals mediated by oxygen free radicals can be monitored by studying the levels of lipid peroxidation in the tissues. The study reported here is to investigate the MDA concentrations in different tissues after various doses of Erycibe obtusifolia (EO) treatments. EO given at doses of 10, 20 and 30 mg/kg body weight is experimentally tested through oral administration. The antioxidant effect of EO extract is assessed by the measurements of hepatic, renal and splenic lipid peroxides (measured as malondialdehyde; MDA) after treatments. The results show no significant time-related and dose-dependent increase or decrease of MDA concentrations in the liver, kidney and spleen after EO administrations, respectively. The peak of antioxidant activities is found on the first day and the 6 hrs after treatments for liver and kidney, respectively. In contrast, the MDA concentrations in spleen after EO administrations remained above the normal values. This result suggests that a high dose of EO administration may contribute a little antioxidant activity in both liver and kidney.