Myelodysplastic syndromes are clonal stem cell disorders, and allogeneic hemopoietic cell transplantation (HCT) is the only therapy with curative potential. Among patients with less-advanced myelodysplastic syndromes, 3-year survivals of 65% to 75% are achievable with human leukocyte antigen (HLA)-identical related and HLA-matched unrelated donors. The probability of relapse is less than 5%. Among patients with advanced disease (> or = 5% marrow blasts), 35% to 45% and 25% to 30%, respectively, are surviving in remission after transplantation from related or unrelated donors. The incidence of post-transplant relapse is 10% to 35%. Criteria of the International Prognostic Scoring System, originally developed for nontransplanted patients, also predict relapse and survival after HCT. Refined conditioning regimens have permitted successful HCT even in patients in their seventh decade of life. Results with a regimen using a combination of busulfan (targeted to predetermined plasma levels) and cyclophosphamide are particularly encouraging. Improved survival with transplants from unrelated volunteer donors reflects selection of donors on the basis of high-resolution (allele-level) HLA typing. Nevertheless, transplant-related morbidity and mortality, including graft-versus-host disease, remain challenges that need to be addressed with innovative approaches. Some patients who achieve a chemotherapy-induced complete remission may also benefit from autologous HCT.