PURPOSE: Blunt aortic injury (BAI) involving the thoracic aorta is usually described as occurring at the isthmus. We hypothesized that injuries 1 cm or less from the inferior border of the left subclavian artery (LSCA) are associated with an increased mortality rate compared with injuries that are more distal. METHODS: A retrospective review of patients admitted with the diagnosis of BAI was performed. Injuries were divided into two groups: group I, injuries that were 1 cm or less from the junction of the LSCA and the thoracic aorta; group II, injuries that were more than 1 cm from the LSCA. Primary outcome measures included cross-clamp time, rupture, and death. RESULTS: In a 14-year period, 122 patients were admitted with BAI. The anatomy relative to the LSCA could be determined in 91 patients who underwent operative repair. Forty-two injuries (46%) were classified as group I, and 49 injuries were classified as group II. Group I injuries were characterized by an increased mortality rate (18/42 or 43% in group I vs 11/49 or 22% in group II, P = .04), intraoperative rupture rate (7/42 or 17% in group I vs 1/49 or 2% in group II, P = .003), and cross-clamp time (39.5 ± 21.9 minutes in group I vs 28.4 ± 13 minutes in group II, P = .04). Three ruptures occurred while proximal control was being obtained. CONCLUSION: Increased technical difficulty and risk of rupture characterize injuries that occur proximally in the descending thoracic aorta, 1 cm from the LSCA. These injuries may be better managed by instituting bypass before attempting to obtain proximal control and by routinely clamping proximal to the LSCA. (J Vasc Surg 2001;34:628-33)