This study was a phase II evaluation of the activity of carboplatin in patients with Philadelphia chromosome positive accelerated or blastic phase of CML. Carboplatin, 250 mg/m2/day as an intravenous continuous infusion was given for 5 days, for a total dose of 1250 mg/m2 per course. If necessary, a second induction course could be given, and patients achieving complete remission were to receive an additional consolidation cycle at the same dose. Thirty-six patients were eligible and evaluable. There were five complete and three partial remissions for an overall response rate of 22% (95% CI 10.1-39.1%). The complete remission rate was 13.9% (95% CI 4.7-29.9%). The median remission duration was 3 months (range 1.4-8.94 months) and the median survival on study for all patients was 3.5 months (95% CI, 2.4-11.4 months). The median survival of responders was 12.8 months (95% CI, 3.6-17.2 months). Three eligible patients survived 2.0, 2.5 and 3.5 years following carboplatin therapy. Carboplatin has activity in blast crisis of CML, but responses are brief. Response did allow one patient to proceed to bone marrow transplantation and two other patients to continue therapy for chronic phase disease before returning to blast crisis. Activity in combination regimens should be explored.