Background: Endovascular treatment of vascular disease involving the descending thoracic aorta has emerged as an alternative to open surgery. However, uncertainty regarding durability and clinical outcome of endovascular treatment have been cited as reasons for caution. We sought to investigate the technical feasibility and the clinical outcome of endovascular stent graft treatment in thoracic aortic aneurysm. Methods: From September 1994 to December 2008, 50 patients (36men, 14women; age 62짹13 years, range 33-86 years) were treated by endovascular stent graft due to aortic aneurysm involving the descending thoracic aorta; aortic aneurysm (n=25) and dissecting aortic aneurysm (n=25). Clinical and imaging follow-up were performed using computed tomography. Results: Follow-up has been completed in 45 patients with a mean time of 50 months (range, 3 to 135 months). The immediate technical success was achieved in 39 of 45 cases (87%). The intentional occlusion of left subclavian artery by stent graft was performed in two patients without complications. Three patients suffered from neurologic complications, 1 from paraplegia and 2 from cerebral ischemia. During follow-up, the overall mortality rate was 4.4% (2 of 45); two cases were no procedure-related events, aortic dissection progression (n=1) and aortoesophageal fistula (n=1) underlying esophageal cancer. Endoleaks (primary endoleaks in 10 cases, secondary endoleaks in 9 cases and recurrent endoleaks in 1 case) occurred in 15 patients (33.3%); Two patients underwent surgical conversion and 3 had additional endovascular procedure. The progression of aneurysm or dissection occurred in 8 patients (17.7%); One patient underwent surgical conversion and 3 had additional endovascular procedure. The aortic rupture occurred in 2 patients and they had additional endovascular procedure without other complications. Conclusions: Endovascular stent graft repair was safe and an effective treatment of thoracic aortic aneurysm that provided favorable technical success and acceptable mid-term results. However, it seems to be important to follow the patients with regular CT scans because of persistent or new endoleaks during follow-up in a minority of treated patients. Keywords: Endovascular treatment, thoracic aortic aneurysm