Background : The aim of this study was to identify whether renin-angiotensin-aldosterone system (RAAS) inhibition after percutaneous coronary intervention (PCI) in latecomers with acute myocardial infarction (AMI) could improve long-term outcomes additionally or not. Methods: A total of 689 AMI patients (63.1짹 12.2 years, 68.8% males) enrolled in a nationwide prospective Korea Acute Myocardial Infarction Registry (KAMIR) between Nov. 2005 and Jan. 2008 who presented between 12 hours and 3 months after symptom onset. The study population underwent successful PCI for total occlusion of the infarct-related artery with poor or no antegrade flow (Thrombolysis In Myocardial Infarction flow 0 to I). The patients were divided into two groups whether prescribed angiotensin-converting enzyme inhibitor (ACEi)/angiotensin-II receptor blocker (ARB) at the time of discharge or not: group I (prescribed, n=579), and group II (not prescribed, n=110). Results: During the one-year follow-up, all cause of death occurred in 19 patients (2.8%). There were no significant differences in age, admission glucose, creatinine (1.02짹1.39 vs. 1.12짹1.07, p=0.312) level, and ejection fraction on periprocedural echocardiogram (43.7짹14.0% vs. 50.8짹11.6%, p=0.164). In terms of coronary artery disease risk factors such as history of hypertension, diabetes mellitus, current smoking and family history, no significant differences existed between two groups. The prevalence of three vessel or left main disease (28.3% vs. 26.4%, p=0.675), Thrombolysis IN Myocardial Infarction flow after procedure (p=0.560), and prescription rate of anti-platelet agent (aspirin, clopidogrel, cilostazol) were similar. By multi-variate Cox regression analysis, there were significant differences in mortality rates between two groups [hazard ratio (HR) = 3.88, 95% CI 1.52-9.90, p=0.005], in case of patients with EF above 40%, significant differences also existed (HR 4.28, 95% CI 1.29-14.1, p=0.017). Conclusion: RAAS inhibition after successful PCI in latecomers with AMI improved long-term clinical outcomes regardless of ventricular systolic function.