Acute coronary syndrome (ACS) is defined as the spectrum of diagnoses from angina to sudden cardiac death caused by ischemic coronary artery disease. Although cardiovascular disease is the leading cause of death of adults in the United States, the ability to diagnose ACS is not always definitive. Cardiac markers are laboratory tests that are used to assist in the diagnosis. Research continues to develop new and refine “old” cardiac markers to improve diagnostic testing that then leads to appropriate and timely interventions for patients with ACS. The purpose of this article is to review the cardiac markers and their role in the diagnosing, as well as predicting the risk of ACS.