In this article we try to determine how frequently emergency physicians (EPs) suspected the diagnosis in acute aortic dissection (AD). In this retrospective descriptive study, we identified all patients with the final diagnosis of AD initially evaluated in 1 of 3 emergency departments (EDs) over a 5-year period. Patients were included if AD was not suspected before ED evaluation. Patients undergoing thoracic aorta imaging as the initial ED study were defined as suspected AD. Forty-three patients totaling 44 presentations were identified. EPs suspected AD in 19 of 44 presentations. EPs suspected AD in 12 of 14 (86%) cases of chest and back pain and in 5 of 11 (45%) of chest pain. Thirteen of 39 (33%) painful presentations involved abdominal pain; EPs suspected AD in 1 of 13 (8%). EPs suspected the diagnosis in 43% of acute AD; location of pain was most predictive of a suspected diagnosis.