This study was performed to investigate the effect of whole mandarin, peel, and pulp intake of Citrus unshiu Marc on the antioxidative capacity of 15-month-old rats. Forty-eight male Sprague-Dawley rats weighing 621.9 $pm$ 10.1 g were separated into four groups according to body weight. The rats were raised with diets containing 5% (w/w) dried mandarin powder for four weeks. Three powders were used, consisting of mandarin peel, pulp, and the entire fruit. Total flavonoids, antioxidant vitamins and dietary fiber was highest in the mandarin peel powder, followed by the whole mandarin powder and the mandarin pulp. The body weight gains of the whole mandarin and mandarin pulp groups were higher, while that of the mandarin peel group was lower than that of the control group. Food intake and ratios of liver, kidney and epididymal fat pad (EFP) weights to body weight were not significantly different among the groups, but ratios of EFP weights per body weight of the experimental groups tended to be lower than that of the control animals. Plasma and liver TBARS concentrations decreased in all the mandarin groups compared to the control group. Plasma and liver xanthine oxidase (XO) activity decreased in all of the mandarin diet groups. Erythrocyte and liver SOD activity in all of experimental groups was not significantly different from the control group. Plasma vitamin A concentration increased significantly in all of the mandarin diet groups. That of the mandarin peel group was 4 times higher than that of the control group. Plasma total carotenoids and vitamin C level also increased in the mandarin peel group. Plasma vitamin I level was not significantly different among the groups.