Background-Thoracic endovascular aortic repair (TEVAR) represents a therapeutic concept for type B aortic dissection.Long-term outcomes and morphology after TEVAR for uncomplicated dissection are unknown. Methods and Results-A total of 140 patients with stable type B aortic dissection previously randomized to optimal medical treatment and TEVAR (n=72) versus optimal medical treatment alone (n=68) were analyzed retrospectively for aortaspecific, all-cause outcomes, and disease progression using landmark statistical analysis of years 2 to 5 after index procedure. Cox regression was used to compare outcomes between groups; all analyses are based on intention to treat. From the University of Rostock, Heart Center and Institute for Biostatistics, Rostock, Germany (C.A.N., S.K., T.C.R., G.K., A.G., T.K., H.I.); CCB Heart Center Frankfurt, Frankfurt, Germany (H.E.); University Heart Center Leipzig, Leipzig, Germany (D.S.); German Heart Institute Berlin, Berlin, Germany (B.Z.); the Centre Hospitalière Universitaire, Hôpital de Rangueil, Toulouse, France (H.R.); the Universitá St. Orsola Malpighi, Bologna, Italy (R.F.); the Department of Cardiovascular Surgery, University Hospital Berne, Berne, Switzerland (M.C.); and Bordeaux Heart University Hospital, Bordeaux, France (L.L.).All members of the Investigation of Stent grafts in Aortic Dissection with extended length of follow-up (INSTEAD-XL) study group are listed in the Appendix in the online-only Data Supplement.The online-only Data Supplement is available at http://circinterventions.ahajournals.org/lookup/suppl