BACKGROUND: It is unknown whether transcatheter valves will have similar durability as surgical bioprosthetic valves. Definitions of structural valve deterioration (SVD), based on valve related reintervention or death, underestimate the incidence of SVD. OBJECTIVES: This study sought to determine and compare the 5-year incidence of SVD, using new standardized definitions based on echocardiographic follow-up of valve function, in intermediate-risk patients with severe aortic stenosis given transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR) in the PARTNER (Placement of Aortic Transcatheter Valves) 2A trial and registry. METHODS: In the PARTNER 2A trial, patients were randomly assigned to receive either TAVR with the SAPIEN XT or SAVR, whereas in the SAPIEN 3 registry, patients were assigned to TAVR with the SAPIEN 3. The primary endpoint was the incidence of SVD, that is, the composite of SVD-related hemodynamic valve deterioration during echocardiographic follow-up and/or SVD-related bioprosthetic valve failure (BVF) at 5 years. RESULTS: Compared with SAVR, the SAPIEN-XT TAVR cohort had a significantly higher 5-year exposure adjusted incidence rates (per 100 patient-years) of SVD (1.61 ± 0.24% vs. 0.63 ± 0.16%), SVD-related BVF (0.58 ± 0.14% vs. 0.12 ± 0.07%), and all-cause (structural or nonstructural) BVF (0.81 ± 0.16% vs. 0.27 ± 0.10%) (p ≤ 0.01 for all). The 5-year rates of SVD (0.68 ± 0.18% vs. 0.60 ± 0.17%; p = 0.71), SVD-related BVF (0.29 ± 0.12% vs. 0.14 ± 0.08%; p = 0.25), and all-cause BVF (0.60 ± 0.15% vs. 0.32 ± 0.11%; p = 0.32) in SAPIEN 3 TAVR were not significantly different to a propensity score matched SAVR cohort. The 5-year rates of SVD and SVD-related BVF were significantly lower in SAPIEN 3 versus SAPIEN XT TAVR matched cohorts. CONCLUSIONS: Compared with SAVR, the second-generation SAPIEN XT balloon-expandable valve has a higher 5-year rate of SVD, whereas the third-generation SAPIEN 3 has a rate of SVD that was not different from SAVR. (The PARTNER II Trial: Placement of AoRTic TraNscathetER Valves - PII A [PARTNERII A]; NCT01314313; The PARTNER II Trial: Placement of AoRTic TraNscathetER Valves II - PARTNER II - PARTNERII - S3 Intermediate [PARTNERII S3i]; NCT03222128).