Background: The efficacy of statin in reducing cardiovascular events are well studied. However, impact of statin in patients with concomitant renal insufficieny and acute myocardial infarction (AMI) is unclear. Methods: A total of 3,935 patients with renal insufficiency (renal insufficiency on admission; defined as estimated glomerular filtration rate < 60 ml/min/1.73m2) diagnosed as AMI was enrolled in a nationwide prospective Korea Acute Myocardial Infarction Registry (KAMIR) from November 2005 to January 2008. All patients were prescribed statin during hospitalization and underwent percutaneous coronary intervention (PCI) with or without coronary stenting. Patients were divided into two groups by prescription of statin: Group I (statin, n = 2,779), Group II (no statin, n = 1,156). End points were major adverse cardiac events (MACE), all-cause of deaths or myocardial infarction (MI), and repeated percutaneous coronary intervention (PCI) during 1-year clinical follow-up. Also, in subgroup analysis, we examined clinical outcomes in patients with severe renal insufficiency (creatinine clearance < 30 ml/min/1.73m2). Results: Group II had more male patients (54.9% vs. 59.2%, p = 0.015) and patients with higher Killip class (III/IV; 16.2% vs. 21.2%, p < 0.001). Cardiovascular risk factors were similar between both groups except dyslipidemia (9.2% vs. 5.3%, p < 0.001) and history of cerevrovascular diseases (10.0% vs. 7.8%, p = 0.026). Group I showed higher baseline level of LDL-C, high-sensitivity CRP than group II. But, baseline left ventricular function, level of proBNP, and cardiac biomarkers were higher in group II. There were no significant differences in rate of patients with ST-elevation MI, and drug-eluting stent implantation between both groups. During hospitalization, aspirin, clopidogrel, cilostazol, anticoagulant, beta blocker, ACE inhibitor or ARB were underused in group II significantly (p < 0.05 respectovely). In-hospital complications including death were more occured in group II (17.8% vs. 22.4%, p = 0.001). During 12-months clinical follow-up, end-points were occurred in 666 patients (21.4%). In Cox-regression analysis, Statin use were associated with reduced MACE (hazard ratio [HR] 0.75, 95% confidence interval [CI] 0.60 to 0.95, p = 0.16), and all-cause of deaths or MI (HR 0.73, 95% CI 0.54 to 0.99, p = 0.048). In subgroup analysis, statin also predicted improved cardiovascular outcomes in patients with several renal insufficiency. Conclusion: Statin improved cardiovascular outcomes in patients with concomitant AMI and renal insufficiency mainly by reducing death or myocardial infarction irrespective of severity of renal insufficiency.