Risk stratifying patients with potential acute coronary syndromes (ACS) in the Emergency Department is an imprecise and resource-consuming process. ACS cannot be ruled in or out efficiently in a majority of patients after initial history, physical exam, and ECG are analyzed. This has led to a reliance on cardiac markers of myocardial necrosis as a key means of making the diagnosis. Commonly used markers, CK-MB and troponin-I, have the drawback of delayed sensitivity. This has led to an ongoing search for one or more marker(s) that would be more sensitive in early ACS. With the central role that platelets play in the pathophysiology of coronary thrombosis, measures of platelet function represent one potential area where an early ACS marker might be identified. This review will focus on selected tests/markers of platelet function that have shown some promise with respect to the risk stratification of patients with potential ACS.