Philadelphia chromosome (Ph) is a translocation abnormality leading to the formation of the BCR-ABL gene rearrangement. This genetic abnormality occurs in up to 30% of adult acute lymphoblastic leukemia (ALL), and its presence is known to be the most adverse prognostic factor for ALL. Because long-term survival cannot be achieved by conventional chemotherapy alone, there is a clear medical need for alternative treatment approaches. Imatinib is a potent selective inhibitor of the BCR-ABL protein kinase, and it has been reported that single-agent imatinib induced response in a substantial proportion of Ph-positive ALL (Ph+ALL) patients, but that the response was not durable. The Japan Adult Leukemia Study Group (JALSG) has therefore started a phase 2 study designed to evaluate the clinical effect of imatinib-combined chemotherapy on newly diagnosed BCR-ABL-positive ALL.