Imatinib Standard Dose (400 mg/Day) Versus Imatinib High Dose (800 mg/Day)

Inclusion Criteria: 1. Age \>/=18 years 2. First chronic phase, less than 6 months of duration 3. High Sokal's risk 4. Ph positive 5. No previous treatment or hydroxiurea only. 6. Performance status (ECOG/WHO) \< 2 7. Written informed consent Exclusion Criteria: 1. Age \<18 2. Low or intermediate Sokal risk score. 3. More than 6 months from diagnosis. 4. Second chronic, accelerated or blastic phase 5. Scheduled allogeneic stem cell transplantation within 1 year from diagnosis. 6. Performance status (ECOG/WHO) \> 2 7. Inability to provide written informed consent 8. Pregnancy 9. Formal refusal of any recommendation of a safe contraception 10. Alcohol or drug addiction 11. Altered hepatic or renal function as defined by AST/ALT or bilirubine \> 3 times upper normal limits (UNL) and by creatinine \> 20mg/L 12. Any other disease or condition that by the advise of the responsible physician would make the treatment dangerous for the patient or would make the patient ineligible for the study, including physical, psychiatric, social and behavioural problems.