In normal controls, essential hypochromic anemia and aplastic anemia, biopsies of the duodenal mucosa were performed for an investigation of the amount of stainable iron and iron uptake by means of radioautography. Followings are the conclusions derived from comparison of these two values. 1. The uptake of radioactive iron into the intestinal epithelium is mild in normal controls and remarkable in essential hypochromic anemia, although no differences were noted following iron treatment. Almost no iron was taken up in aplastic anemia. 2. In general, the amount of non-hemine iron in the intestinal mucosa is invertly proportional to iron absorption rate of the intestinal epithelium. This indicates that the intestinal iron absorption is influenced by the amount of intestinal tissue iron, and the intestinal epithelium, bordering the intestinal cannal, plays an important role in the initial stage of the iron absorption.