A group of 58 children with severe Cooley’s anemia, half of them splenectomized, were reviewed from several of the more important clinical and hematologic aspects. Splenectomy eliminates the extracorpuscular mechanism responsible for the accelerated destruction of normal donor red cells in the patient’s circulation. This represents a lasting improvement and accounts for an increased longevity of normal blood supplements and a striking reduction of transfusion requirements. Less blood was required to maintain at least as good, and at times improved, hemoglobin levels. Estimates of duration of survival of the patient’s own erythrocytes suggest that the basic hemolytic defect is not altered significantly by this operative procedure. While transfusions and splenectomy promote the patient’s well being, growth in height and sexual development are retarded. Secondary sexual characteristics develop, if at all, later than in normal individuals and normal menses are rare. Cardiac failure occurred in 10 patients; all but one had been subjected to splenectomy. This group was characterized by cardiac enlargement, multiple arrhythmias and death with refractory heart failure, usually in the second decade of life. Cardiac complications are likely to be related to the heavy deposition of iron in the myocardium, and are comparable in this respect to a similar incidence in idiopathic hemochromatosis. One of the most serious problems in the management of Cooley’s anemia is the prevention and control of congestive heart failure. This will depend on the discovery of an effective method by which the heart can be made to unload its iron deposits. The increased susceptibility to infection following splenectomy in patients with severe Cooley’s anemia indicates that the normal immunologic responses inherent in the spleen remain intact despite the stress of a continuous hemolytic process.