1. Cyanide inhibited the uptake of vitamin C by human polymorphonuclear leukocytes (PMNs). 2. Preincubation of PMNs with cyanide had no effect on cytochalasin B-inhibitable uptake of dehydroascorbic acid (DHA) (the reversibly oxidized and transportable form of vitamin C). 3. Preincubation of DHA with cyanide resulted in inhibition of DHA uptake. 4. Vitamin C uptake was decreased by cyanide to the same degree as it was by glutathione (GSH), which effectively reduces DHA to ascorbic acid. The effects of cyanide and GSH were not additive. 5. The data are consistent with the hypothesis that cyanide inhibition of vitamin C uptake represents the chemical elimination of extracellular DHA rather than the inhibition of active transport in these cells.