The management of chronic myeloid leukemia (CML) patients who relapse after allogeneic bone marrow transplantation (BMT) is difficult. Hydroxyurea, alpha interferon, second BMT and leukocytes infusion are various options but none of these approaches is clearly optimal. Hydroxyurea controls the symptoms in most patients without any apparent survival benefit. Alpha interferon (IFN) results in haematological remission in most cases with partial or total Philadelphia negativity in 20-30% of patients. Whether IFN therapy prolongs survival is not yet certain. Second BMT results in successful outcome in about half of the patients, however toxicity to the preparatory regimen, post transplant venocclusive disease and acute graft versus host disease are all major complications. An interval of less than 6 months between the initial and second BMT is generally associated with a poor outcome. Buffy coat infusions from the original donor have resulted in a cytogenetic remission in most patients. Less intensive preparatory regimes, donor buffy coat infusion and the use of biological response modifiers post transplant in order to augment the graft versus leukemia effect in high risk patients may indeed be possible areas of improvement in future studies.