Chronic myeloid leukaemia (CML) inevitably terminates in blast crisis (BC) which is of myeloid phenotype in approximately two-thirds and B-lymphoid in one-third of patients. T cell BC is rare and associated with poor prognosis. We describe the case of a 48-year-old woman with extramedullary T cell lymphoblastic transformation. After treatment with combination chemotherapy she achieved a second chronic phase and underwent an allogeneic BMT from an HLA-matched unrelated donor. At 30 months follow-up she is still in complete molecular remission and in good clinical condition. We conclude that unrelated donor BMT should be considered as a therapeutic option for patients with extramedullary BC.