Imatinib, a selective ABL kinase inhibitor has improved therapeutic outcome in patients with Philadelphia positive chronic or acute leukemia. In the present study, we describe a 56-year-old male with Philadelphia chromosome positive acute lymphocytic leukemia (ALL) who was treated with up-front single agent imatinib and achieved complete hematologic, cytogenetic and molecular remission. At relapse 11 months later, new chromosomal translocations involving chromosomes 1, 7 and 4 and cryptic addition to chromosome 11 were identified in Ph+ cells and the patient had rapid deterioration with progressive disease. The significance of additional chromosomal abnormalities in imatinib treated patients and secondary chromosomal abnormalities in Philadelphia positive chronic myeloid leukemia and ALL are discussed briefly in this report.