In this study we evaluated the relationship between the site of the proximal landing zone during endovascular repair of thoracic aortic pathology and treatment outcomes. We reviewed all cases of endovascular repair of thoracic aortic lesions at our institution in the past 42 months. Thirty-seven Talent thoracic endografts were used to treat 20 thoracic aneurysms, 8 intramural hematomas, 6 aortic dissections, and 3 post-traumatic aneurysms. The proximal edge of the covered endograft was situated proximal to the left common carotid artery (zone 1) in 3 patients, between the left common carotid and subclavian arteries (zone 2) in 4 patients, <2 cm distal to the left subclavian artery (zone 3) in 9 patients, and >2 cm distal to the left subclavian (zone 4) in 21 patients. Five patients had extraanatomic bypass to revascularize one or more covered aortic branches. For zones 1, 2, 3, and 4 the endoleak rates were 100%, 0%, 11%, and 0%, respectively; the secondary procedure rates were 33%, 0%, 11%, and 5% respectively; and the treatment failure rates were 67%, 0%, 11%, and 0%, respectively (p < 0.05, for endoleak rates, using Fisher's exact test to compare zone 1 to zones 2, 3, and 4 individually, and as a group). All three endovascular failures were due to proximal type 1 endoleaks. In conclusion, despite the use of great-vessel ligation and extraanatomic bypass to extend the proximal landing zone into the aortic arch, we have been unable to reliably exclude thoracic aortic pathology through use of endografts when the proximal landing zone is proximal to the left common carotid artery.