Chronic myelogenous leukemia (CML) is a progressive and often fatal 
hematopoietic neoplasm characterized by the presence of the Philadelphia 
chromosome. This arises from a balanced translocation between chromosomes 9 and 
22, creating the bcr-abl fusion gene. It is often stated that the only proven 
curative option is allogeneic stem cell transplantation, which is indicated for 
only a limited subset of patients. The Bcr-Abl tyrosine kinase inhibitor 
imatinib represented a major advance over conventional CML therapy. After 
imatinib treatment, > 90% of patients had a complete hematologic response, and 
70%-80% had a complete cytogenetic response. With 5 years of follow-up, the data 
are very encouraging and exhibit a major change in the natural history of the 
disease. The understanding of some of the mechanisms of resistance to imatinib 
has led to a rapid development of new agents that might overcome this 
resistance. The outlook today for patients with CML is much brighter than that 
of a few years ago.