The objectives of this study were to explore the hypotheses that: (1) patients with traumatic rupture of the aortic isthmus (TRA) who have not exsanguinated into the pleural cavity upon hospital presentation are unlikely to develop rupture of the hematoma during the time necessary to investigate all injuries and attend to those of more immediate danger; and (2) appropriate medical therapy can prevent free rupture of the hematoma. The medical records of 112 patients who were proved to have TRA at the isthmus resulting from injury within the preceding 7 days were reviewed. Fifty of these patients received medical treatment aimed at decreasing aortic wall stress; 46 were managed under a formal protocol. The available English language and European literature for the past 15 years was surveyed for evidence of the effects of delay between injury and aortic repair. Eight patients died before aortic repair, six of aortic exsanguination (all within 4 hours of injury). Of 77 patients for whom the time of injury was recorded and the aorta was repaired, 36 were repaired within 12 hours of injury and 41 between 12 hours and 24 weeks; none developed aortic hemorrhage. No patient receiving adequate medical therapy died of rupture of the hematoma. Other major surgery preceded aortic repair in 33 patients. We conclude that the concept that traumatic rupture of the aorta should always take priority over other injuries is incorrect. Pharmacologic reduction of wall stress appears to decrease the probability of rupture of the periaortic hematoma.