The emergency department (ED) evaluation of patients with potential acute coronary syndromes (ACS) has traditionally included initial cardiac marker testing for suspected acute myocardial infarction (AMI). While ED management decisions for patients with ACS have largely been based on history, physical examination, and a presenting 12-lead electrocardiogram (ECG), there is ample evidence that markers impact treatment decisions and provide risk stratification. Newer, more sensitive markers of myocardial necrosis have blurred the distinction between patients with and without classically defined AMI, and have focused attention on the continuum of ACS from angina to transmural Q-wave MI. Newer antiplatelet agents, the glycoprotein IIb/IIIa receptor blockers, are likely to receive increased ED utilization. This use will be partially driven by ED cardiac marker determination. Bedside, point-of-care testing is reliable technology that may shorten time to diagnosis and treatment of ACS in the emergency setting. The ED-based chest pain center (CPC) has become a popular tool to evaluate patients at low- to moderate-risk for ACS and a non-diagnostic ECG. Such centers use serial cardiac marker testing as a mainstay for evaluation and risk stratification. Cost issues have driven many diagnostic patient evaluations from the inpatient setting to such ED observation units. As this becomes more common for low- to moderate-risk patients with chest pain, serial assessment of cardiac markers, and their interpretation by emergency physicians, will become essential.