Background The cornerstones in the assessment of emergency department (ED) patients with suspected acute coronary syndrome (ACS) are patient history and physical examination, electrocardiogram, and cardiac troponins. Although there are several prior studies on this subject, they have in some cases produced inconsistent results. Objective The aim of this study was to evaluate the diagnostic and prognostic accuracy of elements of patient history and the physical examination in ED chest pain patients for predicting major adverse cardiac events (MACE) within 30 days. Methods: This was a prospective observational study that included 1167 ED patients with nontraumatic chest pain. We collected clinical data during the initial ED assessment of the patients. Our primary outcome was 30-day MACE.Results Pain radiating to both arms increased the probability of 30-day MACE (positive likelihood ratio [LR+] 2.7), whereas episodic chest pain lasting seconds (LR+ 0.0) and >24 h (LR+ 0.1) markedly decreased the risk. In the physical examination, pulmonary rales (LR+ 3.0) increased the risk of 30-day MACE, while pain reproduced by palpation (LR+ 0.3) decreased the risk. Among cardiac risk factors, a history of diabetes (LR+ 3.0) and peripheral arterial disease (LR+ 2.7) were the most predictive factors.Conclusions No clinical findings reliably ruled in 30-day MACE, whereas episodic chest pain lasting seconds and pain lasting more than 24 h markedly decreased the risk of 30-day MACE. Consequently, these two findings can be adjuncts in ruling out 30-day MACE.