BACKGROUND CML accounts for 15% of adult leukemia, with incidence ~1 per 100,000. Imatinib mesylate is an oral medication for chronic phase (CP), accelerated phase, or blast crisis phase of CML. For CML patients showing resistance to imatinib, dose escalation is a treatment option. Nilotinib is a second generation tyrosine kinase inhibitor (TKI), rationally designed to preferentially target BCR-ABL, and has demonstrated efficacy and safety in patients resistant or intolerant to imatinib. OBJECTIVES: To estimate the total treatment costs and quality-adjusted life years (QALY) gained for patients receiving high-dose imatinib (HDI) ≥600mg/day because of resistance or nilotinib 800mg/day using a Markov model to project long-term outcome. METHODS: Model parameters were obtained from medical records of patients treated with HDI in Taiwan, along with published clinical trial data for HDI and nilotinib, and local drug and treatment costs. RESULTS: At the end of July, 2008, 45 patients who have received imatinib ≥600mg/day were included in the study and their charts were reviewed. During the entire treatment period of HDI and nilotinib, anemia was the most common treatment-related adverse event (22.2% vs. 15.6%).  The model projected longer expected life-years gained by patients receiving nilotinib therapy (11.72 years versus 9.31 years), and patients treated with nilotinib are expected to experience longer QALY than HDI (9.6 years versus 7.47 years). Estimated cost per QALY was 1,189,150 (NTD/year) for nilotinib and 1,169,547 (NTD/year) for HDI. CONCLUSIONS: Under the assumption of similar drug price for nilotinib and HD imatinib, the benefit of using nilotinib is obvious for the better clinical outcome achieved in terms of lower adverse event rate, better QALY, with acceptable economic impact. The decision of moving therapy from HD imatinib to nilotinib in CML patients with resistance to standard dose imatinib is a reasonable option.