In 117 patients with chronic myelogenous leukaemia (CML) treatment with a combination of high-dose chemoradiotherapy plus transplantation of allogeneic bone-marrow from HLA-identical, mixed-lymphocyte-culture-identical siblings resulted in an actuarial probability of 3-year survival of 63±16% (95% confidence interval) for 39 patients transplanted in chronic phase; 36±14% for 56 transplanted in accelerated phase; and 12±15% for 22 transplanted during blast crisis. Irrespective of disease status at the time of transplantation, and in contrast to chemotherapy, a plateau-effect was observed in the survival curves starting 14 to 19 months after transplantation. The actuarial probability of recurrent or persistent leukaemia at 3 years was 7±9% for patients transplanted in chronic phase, 41+19% for accelerated phase, and 41±39% for blastic phase. All relapses occurred within 18 months of transplantation. This study demonstrates that long-term disease-free survival in CML can be achieved with bone-marrow transplantation. Best results were obtained in patients transplanted during chronic phase of the disease.