BACKGROUND: The Relay Thoracic Stent-Graft with Plus Delivery System (RelayPlus; Terumo Aortic, Sunrise, Fla) was designed to handle the curvature and tortuosity of the thoracic aorta. It was approved by the Food and Drug Administration in 2012; the postapproval study was stopped early because of adequate safety and efficacy data, and no difference was identified in experienced vs first-time users of RelayPlus. The purpose of this study was to report real-world outcomes of patients with thoracic aortic aneurysms and penetrating atherosclerotic ulcers (PAUs) undergoing thoracic endovascular aortic repair (TEVAR) with RelayPlus. METHODS: This is a prospective, multicenter, nonrandomized postapproval study that required the use of novice implanters in the United States. Primary and secondary end points included device-related adverse events (deployment failure, conversion to open repair, endoleaks, migration, rupture, and mortality) and major adverse events (stroke, paraplegia/paraparesis, renal failure, respiratory failure, and myocardial infarction), respectively. Continuous and categorical covariates were reported in means or medians and percentages, respectively. Kaplan-Meier survival estimates were used to report long-term TEVAR-related mortality, all-cause mortality, and reinterventions at 3 years. RESULTS: A total of 45 patients with mean age (standard deviation [SD]) of 73.5 (±7.20) years were treated for descending thoracic fusiform aneurysm (56%) or saccular aneurysm/PAU (44%). The patients were predominantly white (80.0%) and male (68.9%). Mean (SD) proximal neck, distal neck, and lesion lengths were 38.2 (±37) mm, 42.1 (±28) mm, and 103.8 (±74) mm, respectively. Mean (SD) aneurysm, proximal neck, and distal neck diameters were 53.9 (±13) mm, 31.3 (±4) mm, and 31.7 (±6) mm, respectively. Technical success was 100%. TEVAR-related mortality at 30 days was 4.4%; two patients died postoperatively, one of shock and the second of bilateral hemispheric stroke. No patient in the study had any conversion to open repair or post-TEVAR rupture. Two patients experienced three major adverse events, which included stroke (2.2%), paraplegia (2.2%), and respiratory failure (2.2%) at 30 days. Three-year freedom from TEVAR-related mortality, all-cause mortality, and reinterventions was 95.6%, 84.0%, and 97.2%, respectively. There were two type I endoleaks at 3 years: one type IB associated with no migration or aneurysm sac increase and one type IA associated with caudal migration of proximal neck and expansion of the proximal aorta. CONCLUSIONS: The RelayPlus postapproval study reported low operative mortality and morbidity and supported use of the device as a safe and effective thoracic aortic aneurysm and PAU endovascular treatment. Early midterm follow-up showed sustained freedom from TEVAR-related mortality in real-world practice. Follow-up continues to evaluate the durability of this endograft.