Background-Thoracic aortic disease has a high mortality. We sought to establish the contribution of unwarranted variation in care to regional differences in outcomes observed in patients with thoracic aortic disease in England. Methods and Results-Data from the Hospital Episode Statistics (HES) and the National Adult Cardiac Surgery Audit (NACSA) were extracted. A parallel systematic review/meta-analysis through December 2015, and structure and process questionnaire of English cardiac surgery units were also accomplished. Treatment and mortality rates were investigated. A total of 24 548 adult patients in the HES study, 8058 in the NACSA study, and 103 543 from a total of 33 studies in the systematic review were obtained. Treatment rates for thoracic aortic disease within 6 months of index admission ranged from 7.6% to 31.5% between English counties. Risk-adjusted 6-month mortality in untreated patients ranged from 19.4% to 36.3%. Regional variation persisted after adjustment for disease or patient factors. Regional cardiac units with higher case volumes treated more-complex patients and had significantly lower risk-adjusted mortality relative to low-volume units. The results of the systematic review indicated that the delivery of care by multidisciplinary teams in high-volume units resulted in better outcomes. The observational analyses and the online survey indicated that this is not how services are configured in most units in England. Conclusions-Changes in the organization of services that address unwarranted variation in the provision of care for patients with thoracic aortic disease in England may result in more-equitable access to treatment and improved outcomes.