Abstract The leucocyte membrane was found to be permeable to both ascorbic acid and dehydroascorbic acid in either direction. Mean ratios of uptake of dehydroascorbic acid to ascorbic acid by leucocytes of normally fed guinea pigs (1.41 ± 0.16) and of vitamin C-deficient animals (1.91 ± 0.22) are given. No difference in uptake behaviour was observed using leucocytes of animals depleted of vitamin C for up to 16 days. However, ratios for uptake decreased rapidly in leucocytes of such animals being depleted for longer than 20 days, but this was most probably due to inanition and resulting metabolic disorders. After incubation with ascorbic acid, in both groups, only ascorbic acid was found in leucocytes and only ascorbic acid was released during re-incubation. After incubation with dehydroascorbic acid only ascorbic acid was found to be present in leucocyctes of the control group, whereas in the deficient group both, ascorbic acid and dehydroascorbic acid, were found and both compounds were released. After incubation with dehydroascorbic acid in the control group, mainly ascorbic acid was released.