The current study examined the effects of mulberry fruit on the antioxidative defense systems and oxidative stress in the erythrocytes of diabetes-induced rats. Sprague-Dawley male rats were randomly assigned to one normal and three streptozotocin (STZ)-induced diabetic groups. 1be diabetic groups were fed a mulberry fruit-free diet (DM-group), 0.3% mulberry fruit diet (DM-F group) or 0.6% mulberry fruit diet (DM-2F group). Diabetes was induced with STZ after three weeks of the experimental diets. 1be rats were sacrificed 9 days later for examination of the antioxidative defense systems and oxidative stress in the erythrocytes. Means of cy-3-Ο-glucopyranoside, cy-3-Ο-rutinoside, rutin, isoquercitrin, quercetin, morin and dehydroquercetin contents were 230.45, 131.5, 142.5, 10.3, 5.8, 1.6 and 3.83mg per l00g dry weight, respectively, in the mulberry fruit. Mulberry fruit strengthened the antioxidative defense systems through increased activity of the antioxidant enzymes, such as glutathione peroxidase (GSH-px) and catalase (CAT), in the erythrocytes of the diabetes-induced rats. Accrdingly, mulberry fruit was found to reduce the accumulation of thiobarbituric acid reactive substance (WARS). Therefore, mulberry fruit was found to be excellent for strengthening the antioxidative defense system and reducing damaging oxidative substances in the erythrocytes of the diabetes-induced rats.