This clinical policy from the American College of Emergency Physicians addresses key issues in the evaluation and management of patients with suspected non–ST-elevation acute coronary syndromes. A writing subcommittee conducted a systematic review of the literature to derive evidence-based recommendations to answer the following clinical questions: (1) In adult patients without evidence of ST-elevation acute coronary syndrome, can initial risk stratification be used to predict a low rate of 30-day major adverse cardiac events? (2) In adult patients with suspected acute non–ST-elevation acute coronary syndrome, can troponin testing within 3 hours of emergency department presentation be used to predict a low rate of 30-day major adverse cardiac events? (3) In adult patients with suspected non–ST-elevation acute coronary syndrome in whom acute myocardial infarction has been excluded, does further diagnostic testing (eg, provocative, stress test, computed tomography angiography) for acute coronary syndrome prior to discharge reduce 30-day major adverse cardiac events? (4) Should adult patients with acute non–ST-elevation myocardial infarction receive immediate antiplatelet therapy in addition to aspirin to reduce 30-day major adverse cardiac events? Evidence was graded and recommendations were made based on the strength of the available data.