Iron absorption studies with oral 59FeSO4 were performed on 13 iron-depleted, 11 iron-loaded, and 10 control rats, and nonheme iron was determined in both isolated epithelial cells and defoliated mucosa obtained from the duodenum. Mean absorption by the control animals was 18.5% of the dose. Both iron-depleted and iron-loaded groups showed significant differences in iron absorption (54.5% and 2.2% respectively). Compared with the normal controls, iron was decreased in the epithelial cells of the iron-deficient group, whereas higher concentrations were observed in the defoliated mucosa of iron-loaded animals. The latter observation was confirmed by the presence of iron-laden macrophages seen in sections of the lamina propria of the iron-loaded rats.