These studied are designed to evaluate the clinical benefits achieved by iron chelation in patients with chronic iron overload. Detailed assessment of cardiac, endocrine, and hepatic function are performed prior to initiation of chelation therapy and these analyses are repeated annually during the course of iron removal. Desferrioxamine is administered by subcutaneous infusion and the amount of iron removed is determined by quantitation of urinary iron excretion and careful recording of total iron administered by transfusion. Those patients who have no evidence of cardiac disease are randomized to receive either ascorbic acid (3 mg/kg) or placebo.