 Cohorts of 3-6 patients receive escalating doses of irinotecan until the maximum tolerated dose MTD is determined. The MTD is defined as the dose preceding that at which at least 2 of 6 patients experience dose-limiting toxicity. An additional 9 patients with refractoryrelapsed acute myeloid leukemia and 9 patients with chronic myelogenous leukemia in myeloid blast transformation are treated at the MTD. 