Bone marrow from HLA-identical siblings was transplanted in 14 patients with chronic myeloid leukaemia (CML), including one patient in acceleration phase and one in chronic phase following 2 blast crises. Restoration of the bone-marrow occurred in all cases and Philadelphia chromosome could not be detected in any of the patients after the transplantation. Two patients died due to lung complications. Twelve patients who received antiviral prophylaxis (aciclovir per os, anti-CMV-hyperimmunoglobulin) after the transplantation are in very good condition with 140 to 790 days complete clinical and cytogenetic remission. Bone-marrow transplantation, as a curative measure for patients with CML up to the age of 45 (50), should be included in therapy schemes when an HLA-identical sibling is available.