Background.Chronic anemia is common in adults after successful cardiac transplantation. However, the prevalence of anemia in children after cardiac transplantation is uncertain. The purpose of this study was to investigate the prevalence and causes of chronic anemia in well children after cardiac transplantation and in particular to define the role, if any, of iron deficiency, which is important and relatively common in normal children.Methods.Twenty children (ages 7 months to 16 years) who were well 4 months to 6 years after cardiac transplantation were studied. Fourteen children (70%) were anemic and enrolled in a prospective trial of iron supplementation.Results.In the majority of children, serum iron and erythropoietin levels were low, although serum ferritin and zinc protoporphyrin levels tended to be normal or high. Only one child demonstrated a definite response to iron supplementation, although the hemoglobin level remained low.Conclusions.Anemia is highly prevalent in this population, and, despite the presence of low serum iron and transferrin saturation, anemia is not usually due to iron deficiency. Although the diagnosis of iron deficiency in this group is difficult and must not be missed, inappropriate therapy should be avoided. In the majority of children, there appears to be an anemia of chronic disease which may be secondary to chronic inflammation or an effect of cyclosporine on erythropoietin production.