The state of iron deposits in long-term kidney graft recipients is not well-known. Angiotensin enzyme inhibitors (ACEIs) reduce hematocrit levels in patients with posttransplant erythrocytosis (PTE), but their action on iron deposits has not been sufficiently evaluated. We designed this study to investigate the prevalence of iron deficiency among patients without anemia, the efficacy of ACEI treatment and its influence on iron deposits, and the risks of iron treatment in patients with symptomatic iron deficiency but no anemia. One hundred thirty eight patients were included if they had a kidney transplant for more than a year, with good renal function, with no anemia, and with neither iron nor rHuEpo, ARA, or ACEI treatment. One hundred seventeen had a normal Ht (group 1) and 21 had PTE (group 2). Iron deficiency was found in 73 (62.4%) group 1 patients and in 10 (47%) group 2 patients. Two group 1 patients with symptoms of iron deficiency were treated with oral iron. Their symptoms disappeared, but one developed PTE. Enalapril treatment decreased Ht levels in PTE but not in control patients. Furthermore, this drug increased iron deposits in PTE and controls with a baseline iron deficiency. We conclude that there is a high prevalence of iron deficiency in long-term transplanted patients without anemia. Furthermore, iron treatment must be carefully administered because of the risk of PTE. Enalapril treatment decreased Ht levels in PTE but not in control patients and increased iron deposits in patients with baseline iron deficiency.