Myelodysplastic syndromes (MDS) are hemopoietic stem cell disorders, and hemopoietic stem cell transplantation is currently the only therapeutic modality with curative potential. Among patients with less advanced/low-risk MDS (<5% marrow blasts), 3-year survivals of 65--70% are achievable with HLA-identical related and unrelated donors. The overall probability of disease recurrence in these patients is <5%. Among patients with more advanced disease (>or=5% marrow blasts), the relapse probability is higher, ranging from 10--40%, and relapse-free survival is correspondingly lower. The criteria proposed by the International Prognostic Scoring System, derived from non-transplanted patients, also predict survival following transplantation. The development of reduced-intensity conditioning regimens and modification of conventional regimens, all aimed at optimizing the transplant approach, have permitted successful hemopoietic stem cell transplants even in patients 60--70 years of age. Improved survival with transplants from unrelated volunteer donors reflects to a large extent selection of donors on the basis of high resolution (allele-level) HLA typing. Graft-versus-host disease and associated problems remain major challenges after allogeneic transplantation. Autologous stem cell transplantation may be beneficial for selected patients who have obtained complete remissions with conventional chemotherapy.