It is well known that hypertension, aortic dilatation, and collagen disorders predispose to acute aortic dissection (AAD). The inciting events that precede the instant of AAD are incompletely understood. One hundred seventy-five consecutive patients having AAD, treated at our institution during a 10-year period, were reviewed; 65 were women and 110 were men (mean age 61 years). The ascending aorta was affected in 110 patients, and the descending in 65. Information was collected using patients' charts supplemented with direct telephone interviews. Ninety patients were contacted; 65 (24 women, 41 men, mean age 61 years, average aortic size 5.56 cm) could recall specific inciting events for their dissection. In 34 patients, the ascending aorta was involved and in 31 the descending. Eighteen patients (28%) had a positive family history of aortic disease, defined as having > or =1 first-degree relative with aortic disease (aneurysm or dissection). In 24 of the 90 patients contacted (27%), strenuous activity was identified as a clear precipitating factor before the acute onset of thoracic pain; in 36 of 90 (40%) severe emotional stress preceded the onset of dissection pain. Three dissections were iatrogenic. Two additional patients reported a severe exacerbation of chronic obstructive pulmonary disease before their acute onset of chest pain. In conclusion, severe physical and emotional stress may precipitate AAD, presumably on the basis of a transient, severe hypertensive reaction.