Allogeneic bone marrow transplantation (BMT) is the treatment of choice for patients with chronic myeloid leukaemia (CML) who are relatively young and have suitable donors. Relapse is rare more than 5 years after allografting. We describe a patient who relapsed with myeloid blast transformation 14 years after allografting. This case suggests that leukaemia stem cells may on occasion remain quiescent for long periods and emphasises the importance of long-term follow-up after transplantation for CML.