An intensive protocol utilizing mitoxantrone, high-dose cytarabine, vincristine, etoposide and methylprednisolone as induction therapy for chronic myeloid leukemia in blast transformation is described. Fourteen patients were treated, with a remission/second chronic phase achieved in 64%. None of the 3 patients older than 50 yr responded. Complete hematological responses were seen in 9 of the 11 younger patients, 4 of whom also became BCR-ABL negative by Southern Blot analysis. Four patients went on to allogeneic bone marrow transplant. Median remission durations were 4.5 (1-5) and 8.5 (5-16) months in the non-transplanted and transplanted cohorts, respectively. Median survival is 1.5 (0.5-3), 9.5 (7-14) and 17 (14-61+) months in the non-responding, responding non-transplanted and transplanted cohorts, respectively. Toxicity, particularly gastrointestinal, was significant. This represents an aggressive protocol that should be reserved for patients who are potential transplant candidates.