Iron deficiency anemia (IDA) frequently occurs in infants and adolescents. IDA is the result of an interplay between increased host requirements, limited external supply, and increased blood loss. In outpatient clinics, we often see children with iron deficiency anemia. Most cases in children are caused by incomplete nutrient supplements and growth spurts. However, we can occasionally see patients with poor response despite iron supplementation. Failure of iron therapy occurs when a child does not receive the prescribed medication, when iron is given in a form that is poorly absorbed, or when there is a continuing unrecognized blood loss such as intestinal or pulmonary loss, or loss with menstrual periods. In addition, the therapeutic failure of iron medication may indicate that the original diagnosis of nutritional iron deficiency was incorrect. In this situation, we have to evaluate other etiologies of anemia. Recently, many cases relating H.pylori infection to iron deficiency anemia have been described in the literature and H.pylori infection has emerged as a cause of refractory iron deficiency anemia that is unresponsive to oral iron therapy. Also, iron deficiency anemia induced by athletics in adolescent females has been reported several times. In this article, the author reviews various etiologies of childhood iron deficiency anemia. The most important consideration in treatment of iron deficiency anemia is disclosure of the underlying cause and its recovery. Dietary habits should also be corrected. To supplement iron, 6 mg/kg of oral iron supplements (elemental iron) is recommended in ferrous salt form. If oral administration is not feasible, intravenous supplementation is recommended using forms such as iron dextran, iron gluconate, or iron sucrose.