The myelodysplastic syndromes are a heterogeneous group of clonal hematologic disorders characterized by bone marrow failure and proliferation of myeloblastic leukemia cells. Patients with MDS develop cytopenias as a result of ineffective hematopoiesis. These cytopenias are believed to be a result of an increase in apoptosis resulting in an increase in futile cell cycling. In addition, the apparently mature and differentiated hematopoietic cells in patients with MDS are functionally impaired. Granulocytes have decreased myeloperoxidase activity and platelets have impaired function. Therapy for MDS includes supportive care geared mostly to transfusional support. Allogeneic transplantation has been shown to offer the possibility of long-term remission and remains the only curative option for patients with MDS. The development of reduced intensity conditioning regimens expanded the scope of allogeneic transplantation for older patients with MDS. A very large retrospective analysis by the European Blood and Marrow Transplantation Group compared the outcome of 836 patients with MDS treated with either a reduced-intensity conditioning regimen or a conventional regimen before allogeneic transplantation. The 3-year probabilities of progression-free and overall survival were similar in both groups, with a 3-year relapse rate being significantly higher in the reduced-conditioning group, offset by a significantly reduced probability of non-relapse mortality. This demonstrates the importance of the preparative regimen in preventing relapse in this setting.