Two scoring systems are available for disease risk evaluation, Sokal and Euro. Sokal risk is based on chemotherapy treated patients and Euro risk is based on aIFN trated patients: it is not known to date if one or both of the scoring systems will apply to imatinib treated patients. Moreover, the Sokal system has been applied to stratify the patients by risk in all the large clinical trials of imatinib in CML in the last 3 years and consequently, Sokal score will be employed in the present trial.