This is a phase II study to evaluation the capacity of new antileukemic agent, tiazofurin, to induce hematologic remissions in patients with chronic myelogenous leukemia in blast crisis. The relationship between the biochemical and hematologic effects will be examined and the toxicity profile will be assessed. We will examine relationship between biochemical parameters will be assessed on daily blood samples and weekly bone marrow aspirates. Subsequent consolidation cycles will be administered to responding patients.