The data on 1480 bone marrow transplants for chronic myeloid leukemia (CML), performed between 1979 and 1990 were reported to the registry of the European Group for Bone Marrow Transplantation (EBMT). Of these, 1082 patients were transplanted in first chronic phase, 88 in subsequent chronic phase, 251 in accelerated phase and 59 during blast crisis. For these four disease stages leukemia-free survival (LFS) at 5 years is 39%, 22%, 22% and 0%, respectively. A more detailed analysis was performed for 947 patients receiving a first transplant in first chronic phase of their disease from an HLA-identical sibling donor. Survival at 8 years is 47%. At 5 years, relapse incidence (RI) is 33% and the transplant-related mortality rate (TRM) is 42%. The major prognostic factors are patient age (LFS, TRM), T cell depletion (LFS, RI), time from diagnosis to transplant (LFS, TRM), white blood cell count (RI) and donor-recipient sex combination (LFS, TRM). This first report on long-term results of a large cohort of transplanted CML patients confirms and extends previous findings. Stage of disease at time of transplant is the most important prognostic factor. Fifty per cent of all patients transplanted for CML in chronic phase can be expected to be alive at 8 years post-transplant, 40% alive and free of the disease. This number increases to > 60% for patients given cyclosporin and methotrexate without T cell depletion as GVHD prophylaxis. However, there is no plateau phase and late relapses and late transplant-related deaths occur in all subcategories.(ABSTRACT TRUNCATED AT 250 WORDS)