Myelodysplastic syndromes (MDS) are heterogeneous clonal diseases characterized by cytopenias resulting from ineffective hemopoiesis. Anemia affects the vast majority of patients with MDS and contributes substantially to their symptoms. For more than 20 years, recombinant human erythropoietin has been available for clinical use, and it has been employed in an attempt to relieve MDS-related anemia. Erythropoietin-alpha, erythropoietin-beta, and more recently darbepoetin have been found to increase hemoglobin levels and abolish transfusion dependence in 19%-68% of MDS cases. This wide range in clinical response depends on several biological and clinical variables that allow the selection of patients with the highest probability of successful treatment. These agents are a mainstay in MDS therapy, but many issues are still open in terms of the initiation of therapy, the optimal dosage of erythropoietic stimulating agents (ESAs), the most efficient type of ESA, and the duration and outcome of such treatments. In this review, the mechanisms of response and predictive factors as well as an analysis of the clinical activity of ESAs in MDS therapy are presented.