Dasatinib is an inhibitor of BCR-ABL and SRC-family kinases for patients with imatinib-resistant or -intolerant chronic myelogenous leukemia (CML). In this international phase II trial, dasatinib was administered orally (70mg twice daily) to patients with myeloid blast phase (MBP,n=109) or lymphoid blast phase (LBP,n=48) CML. After a minimum follow-up of 12 months (range 0.03-20.7 months), major hematologic responses were induced in 34% (MBP-CML) and 35% (LBP-CML) of patients. Major cytogenetic responses were attained in 33% (MBP-CML) and 52% (LBP-CML) of patients and complete cytogenetic responses were attained in 26 and 46%, respectively. Median progression-free survival was 6.7 (MBP-CML) and 3.0 (LBP-CML) months. Median overall survival was 11.8 (MBP-CML) and 5.3 (LBP-CML) months. Overall, dasatinib had acceptable tolerability. Fluid retention events were more frequent in the MBP-CML than the LBP-CML cohort: pleural effusion occurred in 36 and 13% (all grades) and 15 and 6% (grades 3/4), respectively. Other non-hematologic side effects were primarily grade 1/2; grade 3/4 events were recorded in ≤6% of patients, except febrile neutropenia (15%). Cytopenias were noted in the majority of patients, and were manageable with dose interruptions/reductions. Dasatinib is associated with a promising rate of response in this high-risk population.