Chronic myeloid leukaemia (CML) is characterised by the occurrence of the 
Philadelphia (Ph) chromosome (9/22 translocation) and the formation of a fusion 
protein--the BCR-ABL transcript with constitutive activation of the BCR-ABL 
tyrosine kinase and consequent changes in the intracellular signal transduction, 
which is responsible for the deregulated myeloid cell proliferation. STI571 
(signal transduction inhibition number 571) is a potent and selective inhibitor 
of the BCR-ABL tyrosine kinase. In the chronic phase of the disease, normal 
peripheral blood values are achieved within the first month of treatment in the 
large majority of patients and in many patients also a cytogenic response within 
the following months. The results in the advanced phase are far less favourable, 
which is explained by the development of resistance owing to reactivation of the 
BCR-ABL signal transduction. Side effects are primarily nausea, vomiting, 
various rashes, oedema, most often in the periorbital region, and 
musculoskeletal symptoms, including muscle cramps. Perspectives for treatment 
with STI571 are described, as are combinations with alpha-interferon and other 
cytostatics with a synergistic profile.