The contents of ascorbic acid (AsA) and erythorbic acid (ErA) in the tissues of guinea pigs intraperitoneally injected with AsA and/or ErA were determined to learn the difference in their retention in the tissues. After 10d of AsA depletion, the guinea pigs were intraperi-toneally injected with 5mg of AsA, or 5mg of ErA, or 5mg of each. At day 5 of repletion, the guinea pigs were killed and liver, adrenal glands, spleen, and kidneys were removed. AsA and ErA in these tissues were measured by using HPLC. The contents of AsA in the tissues of only the AsA-injected guinea pigs were similar to those of the AsA- + ErA-injected guinea pigs. The contents of ErA in the tissues of the ErA-injected guinea pigs were higher than those of the AsA- + ErA-injected guinea pigs, but apparently lower than the contents of AsA in the AsA-injected guinea pigs. ErA was scarcely retained in the tissues of guinea pigs.