Transcatheter aortic valve replacement (TAVR) is an alternative to surgical aortic valve replacement (SAVR) in patients with severe aortic stenosis and intermediate or high surgical risk. The aim of this study was to compare the durability of transcatheter and surgical bioprosthetic aortic valves using standardized criteria. In the NOTION (Nordic Aortic Valve Intervention) trial, all-comer patients with severe aortic stenosis and lower surgical risk for mortality were randomized 1:1 to TAVR (n = 139) or SAVR (n = 135). Moderate/severe structural valve deterioration (SVD) was defined as a mean gradient ≥20 mm Hg, an increase in mean gradient ≥10 mm Hg from 3 months post-procedure, or more than mild intraprosthetic aortic regurgitation (AR) either new or worsening from 3 months post-procedure. Nonstructural valve deterioration (NSVD) was defined as moderate/severe patient-prosthesis mismatch at 3 months or moderate/severe paravalvular leakage. Bioprosthetic valve failure (BVF) was defined as: valve-related death, aortic valve reintervention, or severe hemodynamic SVD. At 6 years, the rates of all-cause mortality were similar for TAVR (42.5%) and SAVR (37.7%) patients (p = 0.58). The rate of SVD was higher for SAVR than TAVR (24.0% vs. 4.8%; p < 0.001), whereas there were no differences in NSVD (57.8% vs. 54.0%; p = 0.52) or endocarditis (5.9% vs. 5.8%; p = 0.95). BVF rates were similar after SAVR and TAVR through 6 years (6.7% vs. 7.5%; p = 0.89). In the NOTION trial through 6 years, SVD was significantly greater for SAVR than TAVR, whereas BVF was low and similar for both groups. Longer-term follow-up of randomized clinical trials will be necessary to confirm these findings. (Nordic Aortic Valve Intervention Trial; NCT01057173) Display omitted