Background: Recently the impact of metabolic syndrome (MS) after acute myocardial infarction (AMI) has been interested. In patients with AMI from Korean Acute Myocardial Infarction Registry (KAMIR) in Chonnam National University Hospital who underwent percutaneous coronary intervention (PCI), we sought to determine the prevalence of MS in these patients and its impact on in-hospital outcomes. Methods: A total of 330 patients hospitalized with AMI were categorized according to the modified NCEP ATP III MS criteria (presence of ���3 of the following: hyperglycemia on admission ���110 mg/dL; triglyceride level ���150 mg/dL; high-density lipoprotein cholesterol level <40 mg/dL in men and <50 mg/dL in women; blood pressure ���130/85 mm Hg; and waist circumference >90 cm in men or >80 cm in women). Results: Among the 330 patients, 196 (59.4 %) fulfilled the criteria for MS. The age between the groups were similar and MS group was more likely to be women (15.7 vs. 33.2 %, p<0.001). The incidence of hypertension, dyslipidemia, and glucose level, and BMI were higher in MS group (p<0.001, p=0.008, 0.016, <0.001, respectively). AMI characteristics and left ventricular ejection fraction were similar for both groups. In-hospital mortality was similar between the groups. The clinical in-hospital outcomes of severe heart failure (Killip class >II), cardiogenic shock, and acute renal failure were similar between the groups. The PCI procedural characteristics were similar between the groups. Conclusions: In the selected population of patients with AMI who underwent PCI, the prevalence of MS was high. But, in these patients with MS were not appeared associated with in-hospital mortality and a higher risk of development of worse in-hospital outcomes.