Male Sprague-Dawley rats were fed diets that varied qualitatively and quantitatively in antioxidants. Kidney, heart, lung, and spleen homogenates were incubated at 37°C with and without hydroperoxide or Fe+2. Protection of antioxidants against oxidative damage to tissue was determined by measurement of oxidized heme proteins. Tissues from rats supplemented with dietary vitamin E and selenium showed protection compared to tissues from rats on the basal diet. Tissues from rats with diets containing larger quantities of antioxidants and both fat soluble antioxidants: vitamin E,β-carotene, coenzyme Q10, ascorbic acid 6-palmitate and water soluble antioxidants: selenium, trolox C, acetylcysteine, coenzyme Q0, (+)-catechin, showed the highest protection.