Myelofibrosis is a myeloproliferative disorder characterized by splenomegaly, bone marrow fibrosis and immature white and red blood cells. Allogeneic transplantation is the only curative therapy. In this study, we analyzed the outcomes of 320 patients receiving allogeneic hematopoietic stem cell transplants for myelofibrosis between 1989 and 2002, using the databases of the Center for International Bone Marrow Transplant Research (CIBMTR), a research affiliation of the International Bone Marrow Transplant Registry (IBMTR) and the National Marrow Donor Program (NMDP). This is the largest report of transplantation for myelofibrosis. Patients received a variety of conditioning and graft versus host disease prophylaxis regimens. Most patients received ablative conditioning with either TBI (n=117) or Busulfan (n=150) and cyclophosphamide. Bone marrow was the graft source in 208 patients. 170 transplants were from an HLA-identical sibling donor, 117 from an unrelated donor (MUD), and 33 from an alternative related donor. Median ages at transplant were 45 (<1–73), 47 (1–69) and 40 (<1–65) years, respectively. Median follow up times for survivors were 41 (3–136), 48 (4–124) and 32 (7–118) months, respectively. Both early and long-term survival rates were higher after HLA-identical sibling transplantation. 100-day mortality was 22% after sibling transplants, 42% after MUD transplants, and 27% after alternative family donor transplants. Corresponding 5 year overall survival rates were 39%, 31% and 31%. In multivariate analysis of 215 adult recipients of myeloablative transplants, having an HLA-identical sibling donor, Karnofsky performance score greater than or equal to 90%, younger age, more recent date of transplantation, and absence of blasts in peripheral blood prior to transplantation correlated with better survival. Among 18 patients with all of these favorable factors, the five-year probability of survival was 81%. In conclusion, 1) allogeneic transplantation cures approximately 1/3 of patients with myelofibrosis; 2) young patients with HLA-matched sibling donors have superior survival; 3) results have improved over the last decade. Future research directions will focus on the use of nonmyeloablative conditioning regimens for myelofibrosis.