In the pathophysiological study on the iron-copper metabolism in idiopathic hypochromic anemia the author obtained the following results. 1. In the estimation of the contents of serum iron and copper in the patients with this disease it has been found that serum iron is markedly decreased while serum copper is normal, but showing a marked decrease in the iron-copper ratio. This indicates that in this disease there is a marked change in the iron metabolism while no marked change in the copper metabolism. 2. Iron absorption and intravenous iron injection tests show that this disease demands and utilizes iron actively, and that depending upon the kind of iron administered, the ironabsroption curve is not low, presenting hardly any difference from that of normal persons. In additon, when the change of the serum copper is estimated at the same time, it differs from that of normal persons in that it steadily maintains a certain fixed level. These findings are interpreted to be due to the fact that in the disease such as this which seem to demand iron actively and utilize it immediately as the material for hematopoiesis, a certain fixed amount of copper is always required in order that the hematopoiesis in the bone marrow may function smoothly. 3. There is no great difference in the amount of iron excreted in the urine of this disease as compared with that of normal person, so that it seems not necessary to consider the iron excretion as to be the cause of iron deficiency. Although copper excreted in the urine is somewhat greater than in the case of normal persons, it does not seen to have any significant influence from the standpoint of the copper metabolism. Consequently, the copper metabolism in this disease seems to be carried out rather normally and therefore, copper seems to play no important role directly inducing anemia. 4. In this disease when ACTH is administered intramuscularly, the serum iron content does not change and the serum copper content increases. The amount of iron excreted in the urine tends to decrease while that of copper tends to increase, proving that adrenocortical hormone affects the ironcopper metabolism in this disease. 5. When this disease is treated with Dextran iron, it has a therapeutic effect, and also showing peculiar changes in the contents of serum iron and copper at the time of anemia recovery, it has been confirmed that copper plays a role involving in the iron metabolism of anemia.