In order to pursuit the iron metabolism in the so-called Banti's disease, several investigations about iron metabolism of the erythroblasts in the bone marrow were performed by radioautography and sideroblast examination in the patients with Banti's disease and treated patients with postsplenectomy and administration of iron. Following results were obtained. 1) In the sideroblast staining of the patients with Banti's disease, the grade of appearence of the iron granules in the erythroblasts revealed considerably lower level than that in the healthy persons. In comparison with normal healthy persons, Fe(55) uptake into the erythroblasts in the patients with Banti's disease was markedly increased in vitro and to show that Fe(55) was uptaken by almost all of the erythroblasts and most of cells revealed moderate to markedly high uptake. Above are the similating findings in the essential hypochromic anemia. 2) In the splenectomised cases of 2 months after operation type Ⅰ of the sideroblasts is increased and this tended to show approaching to the normal. While, radioautographically, Fe(55) uptake into the erythroblasts clearly showed to be decreased in the same splenectomised case. In the oral administration of the iron (ferrous gluconate 1 to 2g per day) for 3 months, appearance of type Ⅰ and Ⅱ of the sideroblasts was observed to remarkably high grade and Fe(55) uptake into the erythroblasts showed to be decreased. The erythroblasts that had appeared in high grade tended to show decreasing in number. In the intravenous administration of iron preparate (dextran Fe 100mg/500ml/day) for one week, there were increasing sideroblasts and markedly decreasing Fe(55) uptake into erythroblasts and these tended to show similating finding in the aplastic anemia. 3) As noted already in the various blood diseases, generally, a negative correlation was observed between average number of stainable iron granules and average rate of radioactive iron appearance in the erythroblasts before and after treatments of the patients with Banti's disease; appearance of radioactive iron was observed in high grade in the decreasing condition of the stainable iron granules and also there is a tendency to reveal the reverse findings mentioned above. It is presumed that quantity of non-hemin iron plays an important role in the iron uptake of the erythroblasts.