Any effective antioxidant for vitamin A prevents its oxidation even at the lowest level of the antioxidant to fats and oils containing vitamin A. 10,000 I.U. of vitamin A in each 1g of fish-liver oil (peroxide number about 180) is kept at the room temperature with addition of an antioxidant at 0.1-0.005% to the oil. The blank samples without antioxidant are also kept at the same condition with and without replacement of the air with carbon dioxide. After 2 or 3 days the blank with carbon dioxide shows only 2-4% loss of vitamin A, the blank without carbon dioxide gives nearly 50% destruction of vitamin A and the samples with antioxidant are led to medium destruction between the two blanks. Index of the antioxidant at the given dilution is shown as : Vitamin A of sample with antioxidant-vitamin A of blank. Vitamin A of blank with CO_2 -vitamin A of blank.