By administering orally and paraenterally radioactive iron to the rabbits previously injected with the serum of idiopathic hypochromic anemia, the author obtained the following results. 1. In observing the distribution of radioactive iron in each of non-hemin iron fractions in the liver, spleen, bone marrow and kidneys of the rabbit given the intravenous injection of Fe(59), the radioactivity is highest in the bone marrow and moreover, it is highest in the part one fraction (P(I) fraction). 2. In the observations carried on the disappearance of radioactive iron from blood plasma and appearance in erythrocytes after the oral administration of Fe(55), it appears early and to a higher degree in the plasma but it disappears almost completely within 24 hours as compared with the control. The appearance of it in erythrocytes is likewise rapid and to a high degree, and with lapse of time Fe(55) increases abruptly. 3. Observing the distribution of radioactive iron in the liver, spleen, bone marrow, and duodenum 48 hours after the oral administration of Fe(55), the amount is greatest in the liver, followed by that in the bone marrow, and in the spleen in the order mentioned. In the liver non-hemin iron fractions, P(I) fraction contains the highest radioactivity, and next the P(III) fraction also shows a relatively high value. In the duodenum P(I) fraction contains the highest value and likewise in the spleen it is highest in the same fraction, but no great difference can be observed as compared with the control. From these results obtained by the administration of the serum of this disease the changes of the iron metabolism of rabbit, especially of the non-hemin iron metabolism, seem to be all due to the acceleration of the hematopoietic function in the bone marrow and the increased demand for iron in vivo, and as for the iron absorption in the duodenum it appears there is no disturbance at least from the result of observations in (2), nevertheless, from the increase in the non-hemin iron content observable and from a relatively low specific activity in this organ it seems that the disturbance in the iron absorption can not completely ruled out.