Context: Few studies have examined the association between the number of coronary heart disease risk factors and outcomes of acute myocardial infarction in community practice. Objective: To determine the association between the number of coronary heart disease risk factors in patients with first myocardial infarction and hospital mortality. Design: Observational study from the National Registry of Myocardial Infarction, 1994- 2006. Patients: We examined the presence and absence of 5 major traditional coronary heart disease risk factors (hypertension, smoking, dyslipidemia, diabetes, and family history of coronary heart disease) and hospital mortality among 542 008 patients with first myocardial infarction and without prior cardiovascular disease. Main Outcome Measure: All-cause in-hospital mortality. Results: A majority (85.6%) of patients who presented with initial myocardial infarction had at least 1 of the 5 coronary heart disease risk factors, and 14.4% had none of the 5 risk factors. Age varied inversely with the number of coronary heart disease risk factors, from a mean age of 71.5 years with 0 risk factors to 56.7 years with 5 risk factors (P for trend ≲λτ∀.001). The total number of in-hospital deaths for all causes was 50 788. Unadjusted in-hospital mortality rates were 14.9%, 10.9%, 7.9%, 5.3%, 4.2%, and 3.6% for patients with 0, 1, 2, 3, 4, and 5 risk factors, respectively. After adjusting for age and other clinical factors, there was an inverse association between the number of coronary heart disease risk factors and hospital mortality adjusted odds ratio (1.54; 95% CI,1.23-1.94) among individuals with 0 vs 5 risk factors. This association was consistent among several age strata and important patient subgroups. Conclusion: Among patients with incident acute myocardial infarction without prior cardiovascular disease, in-hospital mortality was inversely related to the number of coronary heart disease risk factors. ©2011 American Medical Association. All rights reserved.