Due to the symptoms, patients with acute type A aortic dissection are first seen by the ambulance service and diagnosed at the emergency department. How often an aortic dissection occurs in an emergency department per year has been studied. The incidence in the emergency department may be used as a quality marker of differential diagnostics of acute chest pain. A multi-institutional retrospective study with the municipal Berlin hospital chain Vivantes and its Department of Pathology and the Charité - University Medicine Berlin was performed. From the Berlin Hospital Society, the annual numbers of publicly insured emergency patients were obtained. Between 2006 and 2016, 631 aortic dissections were identified. The total number of patients treated in the emergency departments (n = 12,790,577) was used to calculate the "emergency department incidence." The autopsy data from six clinics allowed an estimate on how many acute type A aortic dissections remained undetected. Across all Berlin hospitals, the emergency department incidence of acute type A aortic dissection was 5.24 cases in 100,000 patients per year. In tertiary referral hospitals and, particularly, in university hospitals the respective incidences were markedly higher (6.7 and 12.4, respectively). Based on the autopsy results, about 50% of the acute type A aortic dissection may remain undetected, which would double the reported incidences. Among different hospital types the emergency department incidences of acute type A aortic dissection vary between 5.93/100,000 and 24.92/100,000. Aortic dissection; Incidence; Emergency Department; Epidemiology.