This chapter describes the vitamin C transport mechanisms of higher plants and vertebrate animals. Transport systems associated with the plasma membrane of cells mediate absorption. Additional transport systems distribute ascorbic acid and its reversibly oxidized metabolite, dehydroascorbic acid (DHA), among a large number of cells and subcellular compartments, thereby regulating the concentration and redox state of vitamin C in each one. Vitamin C enters and exits cells and subcellular compartments by means of interactions with specific proteins as well as by simple diffusion. Utilization of ascorbate (ASC) as an antioxidant and enzyme cofactor causes its oxidation to DHA in extracellular fluid and cells. DHA has been demonstrated to play important roles in animal and plant cells because it can be used to regenerate ASC and, directly or indirectly, change the redox state of many other molecules. Although the molecular identities of plant vitamin C transporters have not been determined, substantial information exists about the mechanisms of ASC and DHA transport.