Background: Blunt thoracic aortic injury (BTAI) is associated with high mortality. Recent Society for Vascular Surgery (SVS) guidelines recommend repair of all but SVS grade I injuries. This study's objective was to retrospectively determine guideline adherence at the authors' trauma center, and its impact on mortality. Methods: A retrospective review of the trauma database at the authors' university-affiliated trauma center identified and graded all BTAIs between 1999 and 2011. Patient demographics, treatment, and outcomes were recorded. Results: Imaging was available for 52 of 59 (85.2%) patients with BTAI. For these 52 patients, injury distribution was: 14 (27.0%) grade 1; 1 (1.9%) grade 2; 35 (67.3%) grade 3; and 2 (3.8%) grade 4. Nonoperative management was used for 92.8% (13), 100% (1), 34.3% (12), and 0% of grade 1, 2, 3, and 4 injuries, respectively. The operatively managed grade I injury was initially misclassified as grade 3. He was lost to follow-up after discharge. Of the 12 patients with nonoperatively managed grade 3 injuries, 7 (58.3%) died before consideration of endovascular repair and another died early secondary to brain injury. The remaining 4 (11.4%) with nonoperatively managed grade 3 injuries survived to discharge but were lost to follow-up. For grade 3 injuries, endovascular repair was significantly associated with decreased mortality (odds ratio [OR], 0.10; 0.02-0.53; P = 0.007). Exclusion of those with presentation-day mortality negated this significant association (OR, 0.84; 0.07-9.68; P = 1.00). Conclusions: Minor deviation (9.6%) from guidelines did not result in additional morbidity/ mortality. However, a high rate of loss to follow-up limits conclusions. The mortality reduction seen with endovascular repair for grade 3 injury is inflated by patients who die before repair is considered in the nonoperative group. Larger prospective studies with appropriate inclusion and exclusion criteria and improved follow-up are needed to determine the consequences of selective nonoperative management of these injuries.