Iron chelation with deferoxamine was studied in ten patients with sickle cell anemia who had received 2 to 37 liters of red blood cells. Urinary excretion of iron in response to 1.5 gm of deferoxamine administered intravenously ranged from 5.9 to 28.7 mg/24 hours and was closely related to the amount of iron acquired from transfusions. Administration of ascorbic acid did not improve deferoxamine-induced excretion of iron. Urinary excretion of iron in response to 0.75 gm of DFO intramuscularly was 4.7 to 6.9 mg/24 hours in three patients who had received 15 to 37 liters of red cells. The data indicate that measurement of DFO-induced excretion of iron is of value in detecting increased iron stores in children with sickle cell anemia who have received repeated transfusions and that chelation therapy will retard the accumulation of iron.