Oxymetholone was given to 28 adults with chronic anemia from bone marrow disease. Changes in hematocrit and red cell mass were correlated with serial assessments of erythropoietin and erythropoiesis. Erythropoietin excretion was enhanced more than five-fold over the level expected for the hematocrit in 70% of the patients. Only 23% of the patients with an evaluable treatment trial increased their red cell mass by at least 20%. In all responders, the T½ of 59Fe disappearance ranged from 86-136 min and erythron iron turnover exceeded 0.25 mg/100 ml blood/day. A decline in serum iron concentration to the 50-100 µg/100 ml range after 1 mo of oxymetholone was frequently associated with a subsequent response to therapy. Patients with severe bone marrow failure, for whom frequent red cell transfusions were required, did not improve. The failure of other patients to respond was attributed to complicating factors that either impaired maximal erythropoietin production or restricted iron supply to the bone marrow. Hepatic toxicity was detected in less than 10% of treated patients. Results support the use of oxymetholone in the treatment of patients with moderate degrees of bone marrow failure and symptomatic anemia.