 We have started a prospective study of evaluating efficacy and safety of imatinib 600mgday depending on early molecular response in newly diagnosed patients with chronic myelogenous leukemia in chronic phase IDEAL, NCT02204722, which will enroll 150 patients and follow up them for 1 years for the purpose of evaluating the primary endpoints - difference of major molecular response rate at 1 year. However, Chronic myelogenous is a disease which needs long-term for the outcome of treatment with BCR-ABL tyrosine kinase inhibitor. After the end of follow-up period of IDEAL study, subjects who agree with this extension study IDEAL-E will be enrolled and be followed up for additional 4 years to evaluate the duration of treatment response, disease progression, and survival status. Subjects who will be enrolled in this prospective observational study will be treated with drugs - imatinib 300-600mg nilotinib 600mg dasatinib 100mg - which has been chosen by the each investigator according to the drug compliance and overall response. The drug choice will be at the discretion of each investigator, and the overall adverse event molecular response will be monitored every 6 months in this prospective observational study. 