Dehydroascorbic acid is present in insignificant amounts in plant and animal tissue but appears in considerable amounts under various physiological and pathological conditions. It is found increased: in blood of patients suffering from infectious diseases; in blood and tissues of thyrotoxic patients; in blood after injection of thyroxin, corticotropin and cortisone. In all the above conditions there is concomitant decrease in L-ascorbic acid and glutathione values of blood and tissues. Dehydroascorbic acid, however, disappears after continued administration of a high dose of ascorbic acid. The accumulation of dehydroascorbic acid seems to be an indication of ascorbic acid deficiency. The extreme sensitivity of the ascorbate system to physiological changes is suggestive of a major biochemical role for this redox system. Accumulated evidences indicate that dehydroascorbic acid possible control cell division.