AbstractFour patients with idiopathic hemochromatosis were treated with intensive phlebotomy therapy. In 1 to 2 years, 8.8–16.7 g iron was removed. In three out of four patients hemoglobin levels fell at the end of therapy. Serum ferritin was continuously measured during therapy. The greatly elevated serum ferritin levels normalized or decreased to subnormal levels in all patients after therapy. Despite some fluctuations in the first phase of therapy, the fall in serum ferritin was regular with halving of the ferritin levels after about 50% of the excess iron was removed. The normalization of serum ferritin occurred in advance of the hemoglobin decrease at the end of therapy, indicating that in the later stages of therapy the normal iron stores are also depleted. It is emphasized that serum ferritin measurements are useful for monitoring of intensive phlebotomy therapy, and in particular to indicate the end of therapy before anemia develop