Dehydroascorbate (DHA) competitively inhibits the uptake of 2-deoxy-D-glucose and of3-O-methyl-D-glucose by human blood neutrophils; 2-deoxyglucose and 3-0-methylglucose competitively inhibit dehydroascorbate uptake Ratios of Km to KI are near unity for each of these I gands. Exposure of cultured human fibroblasts to insulin enhances cytochalasin B-inhibitable uptake of DHA and of 2-deoxyglucose, both to the same degree. These observations suggest that DHA transport is mediated by glucose transport systems in human neutrophils and fibroblasts.