Normal red cell survival is possible in dialyzed patients. Certain substances like copper and nitratenitrite induce hemolysis if present in the dialysate. We have identified another and probably a more frequent cause for hemolysis in dialyzed patients; chloramines. These compounds (a) are becoming more frequent in tap water as large water plants increasingly use chloramines rather than chlorine as bactericidal agents in tap water; (b) pass reverse osmosis membranes easily; (c) directly induce oxidant damage to red cells with methemoglobin formation; (d) damage the hexosemonophosphate shunt (HMPS) with which red cells defend themselves against oxidant damage; (e) consequently induce hemolysis and short red cell survival time; (f) sensitize the patients to oxidant drugs like primaquine, sulfonamides, etc.; (g) can be removed by charcoal filtration, boiling, or vacuum treatment, and (h) are most expediently neutralized by the addition of ascorbic acid in physiological amounts to the dialysate.