Background: It has been known that triple antiplatelet therapy prevents restenosis after drug-eluting stent (DES) implantation, especially in diabetes patients. However, there are few available data on efficacy of triple antiplatelet therapy for patients with acute myocardial infarction. We compared short-term outcomes between triple antiplatelet therapy (group I, at least 1 month adding cilostazol to aspirin and clopidogrel) and dual antiplatelet therapy (group II, aspirin and clopidogrel) in patients with acute myocardial infarction (AMI) undergoing DES implantation. Major adverse cardiac and cerebrovascular events (MACCE) defined as the composite of cardiac death, non-fatal infarction, re-percutaneous coronary intervention (PCI) and stroke. Methods and Results: We consecutively analyzed 784 patients with AMI undergoing successful DES implantation between November 2005 and February 2007. Among a total of 784 patients, 672 patients (85.7%) were group I and 529 patients (67.5%) were diagnosed with ST elevated MI (STEMI). Mean ages were higher (62.07짹11.86 vs. 59.27짹11.61, p=0.02) and patients diagnosed STEMI were more prevalent (69.0% vs. 58.0%, p=0.02) in group I. There was no significant difference between two groups in 1-month MACCE (3.3% vs. 3.6%, p=0.87), however, group I had significantly lower incidence of 6-month re-PCI and MACCE than group II (9.0% vs 18.3%, p<0.01 and 12.0% vs. 21.1%, p=0.01). TIMI major bleeding events did not occur during follow-up periods, however, one patient suffered from stroke in both groups, respectively. In subgroup analysis, group I had also significantly lower incidence of 6-month MACCE in aged less than 65 years, patients with creatinine clearance more than 60 ml/min, normal LV function and diagnosed with non-STEMI (10.7% vs. 19.4%, 10.3% vs. 18.4%, 9.4% vs. 23.8% and 9.4% vs. 21.3%, p<0.05 respectively). In multivariate analysis, Killip III or IV on admission and triple antiplatelet therapy were the independent predictors of 6-month MACCE (HR=5.733; 95% CI=1.693-19.412, HR=0.302; 95% CI=0.119-0.767) in patients with non-STEMI. Conclusion: Our data show that triple antiplatelet therapy is safe and efficacious in patients with AMI, especially non-STEMI.