Extramedullary blast crisis (EBC) with T-lymphoid phenotype has been reported rarely and generally associated with extremely poor prognosis. We describe a case of T-lymphoid EBC in which long-lasting remission was observed following intensive chemotherapy and allogeneic bone marrow transplantation (BMT). Characterization of bone marrow (BM) and lymph node (LN) cells was performed by means of morpho-cytochemical, cytogenetic, immunophenotypic and molecular analyses. These showed, together with a marrow picture consistent with typical Ph'+ chronic myelogenous leukemia, the expansion of an early T-lymphoid (CD7+/TdT+) LN cell population exhibiting the same bcr rearranged pattern and an additional Ph' chromosome. At the present time, 33 months after BMT, the patient is alive and well, with persistent clinical, hematological, cytogenetic and molecular evidence of complete remission.