Myelodysplastic syndrome (MDS) and myeloproliferative disorders associated with myelofibrosis (MF) are stem cell disorders, and hemopoietic stem cell transplantation (HSCT) is currently the only therapy with curative potential. Among patients with less advanced MDS, 3 year survivals of 65% to 70% are achievable with HLA-identical related and HLA-matched unrelated donors. The probability of relapse is < 5%. Among patients with advanced disease (> or = 5% marrow blasts), about 35 to approximately 45% and 25 to approximately 30%, respectively, are surviving in remission after transplantation from related or unrelated donors. The incidence of post-transplant relapse is 1035%. Criteria of the International Prognostic Scoring System (IPSS), originally developed for nontransplanted patients, also predict survival following transplantation. Patients with MF, either idiopathic or on the basis of pre-existing disorders, are also transplanted successfully with stem cells from related or unrelated donors. Transplants early in the disease, before leukemic transformation, are successful in 60 to approximately 80% of patients. Success rates are lower in patients who have developed MDS or leukemia. New conditioning regimens have permitted successful HSCT even in patients in the 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 may, in part, reflect selection of donors on the basis of high resolution (allele-level) HLA typing. Nevertheless, transplant-related morbidity and mortality, including graft- vs. -host disease, remain challenges that need to be addressed with innovative approaches.