Managing patients with chest pain in the Emergency Department (ED) remains a challenge where advanced imaging technology may play a role. Detecting acute coronary syndrome in the emergency department with cardiac magnetic resonance imaging (MRI) was studied in 161 consecutive chest pain patients in a prospective observational study. Patients with ST elevation myocardial infarction were excluded from study participation. All patients underwent MRI study when hemodynamically stable, free of ongoing chest pain, and within 12 hours of symptoms onset. The MRI study takes an average of 38 +/- 12 minutes and included global and regional left ventricular function, myocardial perfusion, and gadolinium-enhanced myocardial infarction detection. The sensitivity and specificity for detecting acute coronary syndrome was 84% and 85% by MRI. The MRI was more sensitive than strict electrocardiogram (ECG) criteria for ischemia (P < 0.001) and peak troponin-I (P < 0.001). The MRI was more specific than an abnormal ECG (P < 0.001). Multivariate logistic regression analysis showed MRI was the strongest predictor of acute coronary syndrome and added diagnostic value over clinical parameters (P < 0.001). A nonstress cardiac MRI performed in this urgent clinical setting is safe and exhibited diagnostic operating characteristics suitable for triage of patients with chest pain in the emergency department. MRI accurately detected a high fraction of patients with acute coronary syndrome including patients with enzyme negative unstable angina.