Although widely used in Europe, the prehospital 12-lead electrocardiogram (EKG) has seen only limited use in this country. Reported benefits of the 12-lead EKG include shortening the door-to-needle time, accelerating the initiation of reperfusion therapy, and overall improving the prehospital and hospital management and outcome of patients with acute myocardial infarction. The field EKG also provides the basis for prehospital fibrinolysis. Concerns still exist, however, regarding the best means of providing real-time field interpretation of the prehospital EKG and the potential for inappropriate field time delay, triage, and treatment of patients. Moreover, questions remain about the overall clinical and cost benefit of expanding this resource universally. The following article reviews the role of prehospital EKG in caring for patients with acute coronary syndromes.