This study was performed to investigate effects of hesperidin and naringin on linpid peroxide formation and antioxidative enzyme activities in rats. Thiobarbituric acid reactive substance (TBARS) concentrations were measured in plasma and liver. Catalase, superoxide dismutase, and glutathione peroxidase activities were measured in erythrocyte and liver. Forty-nine male Sprague-Dauley rats weighing 275.3$pm$3.3g were blocked into seven groups according to body weight and were raised fro four weeks on diets containing 0.25, 0.50 or 1.00%(w/w) hesperidin or naringin . Food intake, weight gain , food efficiency ratio, and weights of liver, kidney, spleen ,and epididymal fat pad were not significantly different among groups. In 0.50 and 1.00% naringin groups , plasma TBARS concentrations were significantly decreased with a dose response patter. In 0.25, 0.50 and 1.00% hesperidin groups, liver TBARS concentrations were significantly decreased without a dose dependent patter. Antiosidative enzyme activities in erythrocyte and liver were not significantly affected by type and amountof dietary bioflavonoid, but in the 1.00% hesperidin group, catalase, superoxide dismutase, and glutahione perosidase activities in linver showed a tendency to increase. In conclusion, naringin inhibited lipid peroxide formation with a dose response pattern in plasma without changing the activities of antioxidative enzymes. Hesperidin adminstration, regardless of the level in the diet, inhibited lipid peroxide formation in liver.