This study was designed to evaluate the effects of dietary vitamin E and caffeine on the activities of lipid peroxidation related enzymes in rat liver . Male Sprague-Dawley rats were fed on diets containing three level of vitamin E (37.5, 750 or 1,5oomg/kg diet) and with or without 0.3% caffeine. The rats were sacrificed after 5 and 10 weeks of feeding. Results obtained from this study were as follows ; The content of cytochrome P450 tended to increase as dietary vitamin E level was raised. The activity of xanthine oxidase increased in the caffeine groups, but it decreased by the increasing level of vitamin E. Superoxide dismutase and catalase activity were slightly elevated by dietary supplementation of vitamin E. And there was a tendency of higher these enzyme activity of caffeine groups. The activity of glutathione perxidase tended to decrease as dietary vitamin E level increased. But it was raised by caffeine supplementation . Liver glutathione content was not affected by dietary supplementation of vitamin E, but it showed a decreasing tendency in caffeine groups. There was a tendency of more lipid peroxide content of caffeine groups than that of the only vitamin E supplemented group. But the degree of increment of this decreased as dietary vitamin E level increased.