OBJECTIVE: This study was carried out to evaluate the long-term cost-effectiveness of clopidogrel in addition to aspirin in Acute Coronary Syndromes (ACS) in South Korea. METHODS: A cost-effectiveness analysis was conducted from the societal perspective and incremental cost-effectiveness ratios (ICER) were estimated using a long-term Markov process model, in which transition probabilities were estimated through the survival analysis using the Korean health insurance claims and the cause of death registers data. Treatment effects were based on the ‘Clopidogrel in Unstable Angina to prevent Recurrent ischemic Events (CURE)' trial and it was assumed that patients were treated for one year. The costs included direct and indirect costs as well as cost in added years of life and were estimated from the Korean health insurance claims and the National Health and Nutrition Survey. Both costs and effectiveness were discounted by 5%. Sensitivity and subgroup analyses were conducted on the discounting rate and on the baseline population structure to test the robustness of the results. RESULTS: In the base case scenario, the model predicted a longer survival in the ‘clopidogrel in addition to aspirin' arm (7.705 years vs. 7.439 years incremental LYG=0.266 years) and higher costs in the ‘aspirin alone' arm (6,944,249 vs. 6,876,536 Korean Won; incremental costs=67,713 Kwon)(US $1 = approximately 1000 Korean won). The cost was lower while the effectiveness was better; therefore, the ‘clopidogrel in addition to aspirin' arm was dominant over ‘aspirin alone' arm in cost-effectiveness. Sensitivity and subgroup analyses showed that ‘clopidogrel in addition to aspirin' remained cost effective regardless of the population structure and discount rate change. CONCLUSIONS: The combination clopidogrel with aspirin is cost effective in patients with ACS in South Korea compared to aspirin alone.