Thus, it is not known whether severely ill patients are likely to respond to iron alone, or addition of erythropoiesis-stimulating agents (ESA) is also necessary. The present study was designed to assess the magnitude and time course of the hematologic response to treatment with the combination of erythropoietin and intravenous iron versus intravenous iron alone, in iron-deficient anemic patients with advanced-stage HF. Forty-three consecutive anemic patients with advanced HF due to ischemic or dilated cardiomyopathy, recently hospitalized for HF decompensation, were screened. Anemia was defined as serum hemoglobin (Hgb) <12 g/dl in men and <11.5 g/dl in women. All patients underwent the standard diagnostic workup, including bone marrow aspiration, to determine the cause of their anemia. Thirty patients identified with ID (mean age: 57.3 ± 11.7 years, NYHA functional class: 3.3 ± 0.8, Vo2 at peak exercise: 13.5 ± 4.9 ml/kg/min, left ventricular ejection fraction: 24 ± 6.9%, left ventricular end-diastolic diameter: 71.8 ± 8.0 mm, pulmonary capillary wedge pressure: 25.4 ± 9.2 mm Hg, and cardiac index: 1.8 ± 0.3 l/min/m2) were enrolled in this study.