We are prompted to make this report because the cases to be described seem to represent a disorder of the blood in adolescents and adults which has hitherto received little attention. It is a chronic disturbance of erythropoiesis which is marked by microcytosis and hypochromia and by the production of red corpuscles of bizarre shape and red cells resembling targets. Normoblasts, polychromatophilic and particularly stippled red cells are found in the circulating blood. These abnormalities occur in spite of the presence of little or no anemia and even in the face of an actual increase in the red cell count above normal. The red corpuscles possess an unusually great resistance to destruction in hypotonic solutions of sodium chloride, yet there may be some evidence of increased red cell destruction in vivo. The patients may have no complaints, but splenomegaly is often found and roentgenographically demonstrable changes in the bones may