Background: The purpose of this study was to investigate the clinical usefulness of myocardial contrast echocardiography (MCE) to distinguish stress-induced cardiomyopathy (SCMP) from acute myocardial infarction (AMI) in the emergency department (ED). Methods and Results: We investigated 51 patients (62±13 years, 29 women) who had suspected SCMP in the ED with acute chest pain and showed apical wall motion abnormality on 2-dimensional echocardiography. All patients were assessed by real-time MCE and the perfusion status and quantitative myocardial perfusion parameters were analyzed. After MCE, coronary angiography was performed within 24h. Of 51 patients, 27 had significant perfusion defects (group A) and 24 had preserved perfusion at the apex (group B) by MCE. In group A, 25 patients showed significant luminal stenosis in the left anterior descending artery (LAD) and 2 patients showed no critical luminal stenosis. In group B, 20 patients showed no luminal stenosis and 4 patients showed moderate LAD stenosis. Sensitivity, specificity, positive and negative predictive values of MCE for detection of SCMP were 91%, 86.2%, 83%, and 93%, respectively. Quantitative MCE parameters were significantly decreased in group A compared with group B. Conclusions: Myocardial perfusion measured by MCE is relatively preserved in patients with SCMP compared with those with AMI. Therefore, real-time MCE may be a useful noninvasive diagnostic tool to distinguish SCMP from AMI in the ED. (Circ J 2012; 76: 1393-1398)