Background: The renin-angiotensin-aldosterone system blockades have been shown to improve clinical outcomes in patients with heart failure and acute myocardial infarction (AMI). This study sought to assess the efficacy of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) in patients with AMI and preserved left ventricular (LV) systolic function. Methods: As part of the Korean Acute Myocardial Infarction Registry (KAMIR), 1989 AMI patients (61.1짹12.1 years, male 74.2 %) with left ventricular ejection fraction > 50% and a serum creatinine concentration of ��� 1.5 mg/dl were enrolled from Nov. 2005 to Dec. 2007. were enrolled. All patients underwent percutaneous coronary intervention which attained Thrombolysis in Myocardial Infarction flow grade 3. The patients were divided into three groups: ACEI group (n=1445), ARB group (n=241), and control group (no ACEI or ARB) (n=303). The clinical characteristics and in-hospital adverse events (IHAEs) were compared among the groups. Results: The clinical diagnosis, laboratory parameters, and strategy of treatment were similar among the groups. The prevalence of hypertension and diabetes were the highest in the ARB group. The rate of Killip class III/IV and complex lesion were the highest in the control group. The use of cilostazol or beta blockers after discharge was the most in the ACEI group. At 1 month and 6 months, the composite major adverse cardiac events (MACEs) were not different among the groups (2.4% vs. 2.1% vs. 2.6%, p=0.912; 10.5% vs. 12.9%vs. 9.9%, p=0.489, respectively). However, the rates of coronary artery bypass graft (0.0 % vs. 0.8 % vs. 0.3%, p=0.006) and target lesion revascularization (TLR) (4.2% vs. 6.6 % vs. 2.0%, p=0.025) were the highest in the ARB group. Rate of total MACEs at 12 months was no significant difference among the groups (13.3% vs. 15.4% vs. 12.5%, p=0.603). As compared with the control group, the ACEI group had no different rates of total MACEs and TLR at 1, 6, and 12 months, however, the ARB group had a higher rate of TLR at 6 (6.6% vs. 2.0%, p=0.006) and 12 months (71.% vs. 3.0%, p=0.027). In Cox proportional hazard regression analysis, the use of ARB was associated with TLR at 6 (RR: 1.87, 95% CI 1.16-3.02, p=0.008) and 12 months (RR: 1.57, 95% CI 1.04-2.38, p=0.004) in AMI patient with preserved LV systolic function. Conclusion: ACEI or ARB has not beneficial effect for improvement of clinical outcomes in AMI patients with preserved LV systolic function.