Feeding of 100 000 I.U. of Vitamin A on alternate days, five times to rats, resulted in a marked lowering in in vitro lipid peroxidation of the tissue hemogenates. alpha-Tocopherol or DPPD supplementation along with A still further reduced the in vitro lipid peroxidation of the tissues. Vitamin A in large doses increased the antioxygenic potential of the tissues, and it is suggested that retinol also might be considered as a potential antioxidant similar to tocopherol in animal nutrition.