Obstructive sleep apnea syndrome (OSAS) is a process that is associated with the development of arterial hypertension, the main risk factor for aortic dissection and during obstructive episodes of the upper airways with marked increases in transmural pressure of the aorta wall. The aim of this work was to study the association between aortic dissection and OSAS. Nineteen consecutive patients with thoracic aorta dissection and 19 hypertensive patients of similar age, sex, and body mass index were studied by clinical questionnaire and polysomnography. Snoring and nonrefreshing sleep were common in both groups. Thirteen patients (68%) from each group showed an apnea-hypopnea index of more than 5 per hour. However, patients with aortic dissection presented a higher apnea-hypopnea index (28 [30.3] versus 11.1 [10.4], p=0.032). Seven patients with dissection presented an apnea-hypopnea index of more than 30 versus 1 patient in the control group (p=0.042). Patients with thoracic aorta dissection presented a high prevalence of previously undiagnosed and frequently severe OSAS. Further studies, including this diagnosis as a prognostic variable in the follow-up of patients with aortic dissection, are required. Our results suggest that in patients with aortic dissection and symptoms consistent with OSAS, a sleep study should be considered in their clinical management.