Background Despite strong evidence linking decreased glomerular filtration rate (GFR) to worse outcomes, the impact of GFR on mortality and morbidity in patients with acute myocardial infarction (AMI) is not well defined. Study Design Retrospective cohort study. Setting & Participants 12,636 patients with AMI in the Korea AMI Registry database from November 2005 to July 2008. 93% of patients in this registry had coronary angiography, and 91% of patients with coronary angiography had percutaneous coronary intervention (PCI). Predictor GFR was estimated (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, and patients were grouped into 5 eGFR categories: >90, 60-89, 30-59, 15-29, and 2 . Outcomes Primary end points were death and in-hospital complications. Secondary end points were major adverse cardiac events (MACEs) during a 1-month (short-term) and 1-year (long-term) follow-up after AMI. Results Mean eGFR was 72.8 ± 24.6 mL/min/1.73 m 2 , mean age was 64 ± 13 years, and 70.4% were men. A graded association was observed between eGFR and clinical outcomes. In adjusted analyses, compared with eGFR >90 mL/min/1.73 m 2 , patients with eGFR of 30-59, 15-29, and 2 experienced increased risks of short- (respective HRs of 2.30 [95% CI, 1.70-3.11], 3.10 [95% CI, 2.14-4.14], and 3.64 [95% CI, 2.44-5.43]; P P Limitations Single assessment of serum creatinine. Conclusion eGFR was associated independently with mortality and complications after AMI. PCI, β-blocker, ACE inhibitor or ARB, and statin use were associated with decreased risks of short- and long-term MACEs.