Background: The Navitor transcatheter heart valve (THV) is a self-expanding valve, with an intra-annular leaflet position and an outer cuff intended to reduce paravalvular leak (PVL). Aims: The aim of the PORTICO NG Study is to assess the safety and performance of the Navitor THV in patients with symptomatic, severe aortic stenosis who are at high or extreme surgical risk. Methods: PORTICO NG is a prospective, multicentre, global, single-arm, investigational study with follow- up at 30 days, 1 year, and annually up to 5 years. The primary endpoints are all-cause mortality and moderate or greater PVL at 30 days. Valve Academic Research Consortium-2 events and valve performance are assessed by an independent clinical events committee and echocardiographic core laboratory. Results: A total of 120 high- or extreme-risk subjects (age 83.5±5.4 years; 58.3% female; Society of Thoracic Surgeons score 4.0±2.0%) were enrolled in the European conformity (CE) mark cohort. Procedural success was high at 97.5%. At 30 days, the rate of all-cause mortality was 0%, and no subjects had moderate or greater PVL. The rate of disabling stroke was 0.8%, life-threatening bleeding was 2.5%, stage 3 acute kidney injury 0%, major vascular complications 0.8%, and new pacemaker implantation 15.0%. At 1 year, the rates of all-cause mortality and disabling stroke were 4.2% and 0.8%, respectively. The rate of moderate PVL was 1.0% at 1 year. Haemodynamic performance with a mean gradient of 7.5±3.2 mmHg and effective orifice area of 1.9±0.4 cm2 was sustained up to 1 year. Conclusions: The PORTICO NG Study demonstrates low rates of adverse events and PVL up to 1 year in patients at high or extreme surgical risk, confirming the safety and efficacy of the Navitor THV system. © Europa Digital & Publishing 2023. All rights reserved.