A group of 14 infants and children with nutritional iron-deficiency anemia were studied with respect to gastrointestinal function and structure both before and after iron treatment. A high incidence of abnormalities was found, consisting of gastric achlorhydria, impaired absorption of xylose and vitamin A, and steatorrhea. Duodenal biopsies revealed varying degrees of chronic duodenitis and mucosal atrophy. There was poor correlation between structure and function. Following treatment with oral iron most of the abnormalities reverted to normal. A control group of 8 children with long-standing anemias not due to iron deficiency were subjected to similar studies, most of which yielded normal results. These observations indicate a diffuse and reversible enteropathy in children as a result of iron deficiency. The pathogenesis and practical implications are discussed.