Patients with malignant diseases frequently develop anemia. An alternative to blood transfusions is the application of recombinant human erythropoietin. Several nonrandomized and prospective, placebo-controlled studies have demonstrated the effect and safety of erythropoietin in patients with hematological malignancies, particularly in patients with multiple myeloma and low- to intermediate-grade non-Hodgkin's lymphoma. However, in patients with myelodysplastic syndromes, the rather low response rate of erythropoietin is overcome by the combination of erythropoietin with granulocyte colony-stimulating factor. A significant acceleration of the reconstitution of erythropoiesis has been reported in allogeneic, but not in autologous bone marrow transplantation. Especially in large open-label, multicenter studies, a statistically and clinically significant improvement in quality of life independent from chemotherapeutic response or tumor type has been demonstrated. A number of simple algorithms have been proposed using the pretreatment serum erythropoietin level, transfusion requirements, and early changes in hematological parameters.