Four cases of severe refractory anemia with an enormous increase of demonstrable free iron in the normoblasts are reported. Three cases were of unknown etiology and of benign course but in the fourth the anemia was probably related to rheumatoid arthritis or to the onset of myeloblastic leukemia. The significance of the sideroblastic bone marrow in these cases is discussed and the opinion expressed in the literature—that it indicates a defect in hemoglobin synthesis is subscribed to. Thus, it is believed that the anemia in these cases is due to degenerative changes in the bone marrow which also have some morphologic manifestations. The disturbance of marrow activity is probably best reflected in the reticulocyte counts.