Summary The judicious administration of an antianemia agent implies not alone the restoration of normal blood levels but an inquiry into the pathogenesis of the anemia with a view to correcting the underlying cause. In this paper the treatment of anemias was integrated with a consideration of etiology and diagnosis. In infants, for instance, the basis of an anemia requires a search of the fetal period for an appraisal of the adequacy of iron storage, for evidences of maternal isoimmunization by fetal blood elements, for anemia in the mother, and for possible extrinsic causes which may have interfered with the normal continuity of antenatal development of the blood-forming organs. In contrast to adults, in whom blood levels are static, reference must be made to normal hematic values of corresponding periods of growth in determining the need for treatment and the efficacy of an antianemia agent in infants and children. Pending recognition of the nature of the anemia, interim treatment may be given. Orientation can be facilitated by employing data from indirect sources. The relationships between the red cell count, hemoglobin, and the volume of packed red cells offer important clinical clues to treatment. The mean corpuscular volume and the mean corpuscular hemoglobin concentration are practical guides for diagnosis and therapy in various groups of anemias. Conversely, the color index may prove unreliable in infants and children because of the physiologic fluctuations in hemoglobin and red cell counts with age. Recent advances in iron, folic acid, and transfusion therapy were reviewed in relation to the anemias of infancy and childhood. In common with all age periods, these advances have been marked by a greater selectivity of wellestablished drugs rather than by the addition of new antianemia agents. The choice of treatment of erythroblastosis by replacement or repeated small transfusions was discussed. A review of the methods and major indications for exsanguination transfusion indicate that many aspects of this form of therapy are in the process of development and evaluation. The organization of an outpatient transfusion clinic for the treatment of chronic anemias was described. The benefits to the anemic child and the practical advantages to hospital administration have been amply shown in the experiences at the New York Hospital. In the therapy of the group of aplastic anemias, it was pointed out that chronic congenital aregenerative anemia should be separated as a hematologic entity distinct from hypoplastic anemia. The evidence in a case history that was cited suggested that the pathogenesis of chronic congenital aregenerative anemia, an unusual blood disorder, might be related to early isoimmunization with a blood-group factor in an incompatible pregnancy. The hypothesis that a depression in red cell production results from an antigen-antibody reaction occurring in fetal life is far-reaching and requires further investigation. Finally, the specific treatment of the common anemias in infancy and childhood was summarized in conjunction with the diagnostic features of the respective blood smears.