Sixteen patients receiving long-term hemodialysis therapy demonstrated a decline in leukocyte ascorbic acid concentration of 26% during a single hemodialysis. Eight patients receiving 1 gm of ascorbic acid by mouth showed a 76% rise in leukocyte ascorbic acid concentration in three hours, while control subjects showed a 5% increase. When ascorbic acid was added to dialysate baths of 12 patients, plasma ascorbate levels were elevated by 26% at the end of dialysis, and leukocyte levels rose by 11%. Short-term hemodialysis therapy over five consecutive days produced a continuous decline in plasma and leukocyte ascorbate levels. Ascorbic acid loss from leukocytes and plasma during hemodialysis can be prevented by the addition of the vitamin to dialysate concentrate.