A study of reutilization of iron by means of Fe59-tagged hemoglobin solution given to normal individuals yielded a rate of reutilization of 70 per cent or more, evidence perhaps that the active storage pool of iron at a given moment is not larger than the plasma iron compartment. Reutilization of iron in patients with anemia complicating malignancy disease has shown a significant decrease which correlates well with the severity of the anemia.