4NEMIAS COMPLICATING MALIGNANT NEOPLASMS may be seekt ondary to blood loss, increased blood destruction, invasion of the hemopoietic organs or represent a side effect of the myelo-depressive agents used in the treatment of the neoplasm. Often none of these etiologic factors can be demonstrated. The anemia is usually mild to moderate in severity (8 to 10 Gm. per cent ) and, less frequently, severe ( 7 Gm. per cent or less ) . The reticulocyte count is usually within normal limits. The red blood cells are normocytic. Mild to moderate degree of hypochromia of the red blood cells, not uniformly present, is often found upon examination of the peripheral blood smear. The bone marrow examination reveals normal cellularity with adequate erythroid activity. Erythrokinetic studies including radioiron clearance, red cell radioiron utilization, intestinal absorpton of iron and Cr51-tagged red blood cells survival14’23 often do not help in clarifying the mechanism of the anemia which remains obscure. Since the serum iron level is usually low despite increased iron stores5 and the anemia is not corrected by administration of iron orally, it was thought likely that a study of the degree and mode of reutilization of the iron already available in the body might be helpful in understanding the mechanism of the anemia. Freireich et al.6 has found poor reutilization of iron in dogs subjected to turpentine-induced inflammation. This paper reports the results of the attempts at such a study in patients with malignant diseases, and the implications of the findings.