The European Bone Marrow Transplant Leukaemia Registry has collected data from 52 European centers between 1979 and 1986. More than 2,000 transplants performed for a haematological malignancy were reported. The present analysis shows that the most important factor influencing leukaemia free survival, transplant related mortality and relapse incidence is the stage of the disease at the time of the transplant. Outcome is highly better when the transplant is performed for acute myeloid and acute lymphocytic leukaemia in first complete remission and for chronic myelocytic leukaemia in first chronic phase. Additional prognostic factors are age, the method for graft-versus-host disease prevention and the donor recipient sex combination. Results are better for younger patients, for patients given cyclosporine for prevention of graft-versus-host disease and are worse for male patients receiving a female donor bone marrow. The results are not influenced by the year of the transplant per se and by the center size.