Background: The SYMPLICITY HTN-3 (Renal Denervation in Patients With Uncontrolled Hypertension) trial showed the safety but not efficacy of the Symplicity system (Medtronic, Santa Rosa, CA, USA) at 6 months follow-up in patients with treatment-resistant hypertension. This final report presents the 36-month follow-up results., Methods: SYMPLICITY HTN-3 was a single-blind, multicentre, sham-controlled, randomised clinical trial, done in 88 centres in the USA. Adults aged 18-80 years, with treatment-resistant hypertension on stable, maximally tolerated doses of three or more drugs including a diuretic, who had a seated office systolic blood pressure of 160 mm Hg or more and 24 h ambulatory systolic blood pressure of 135 mm Hg or more were randomly assigned (2:1) to receive renal artery denervation using the single electrode (Flex) catheter or a sham control. The original primary endpoint was the change in office systolic blood pressure from baseline to 6 months for the renal artery denervation group compared with the sham control group. Patients were unmasked after the primary endpoint assessment at 6 months, at which point eligible patients in the sham control group who met the inclusion criteria (office blood pressure ≥160 mm Hg, 24 h ambulatory systolic blood pressure ≥135 mm Hg, and still prescribed three or more antihypertensive medications) could cross over to receive renal artery denervation. Changes in blood pressure up to 36 months were analysed in patients in the original renal artery denervation group and sham control group, including those who underwent renal artery denervation after 6 months (crossover group) and those who did not (non-crossover group). For comparisons between the renal artery denervation and sham control groups, follow-up blood pressure values were imputed for patients in the crossover group using their most recent pre-crossover masked blood pressure value. We report long-term blood pressure changes in renal artery denervation and sham control groups, and investigate blood pressure control in both groups using time in therapeutic blood pressure range analysis. The primary safety endpoint was the incidence of all-cause mortality, end stage renal disease, significant embolic event, renal artery perforation or dissection requiring intervention, vascular complications, hospitalisation for hypertensive crisis unrelated to non-adherence to medications, or new renal artery stenosis of more than 70% within 6 months. The trial is registered with ClinicalTrials.gov, NCT01418261., Findings: From Sep 29, 2011, to May 6, 2013, 1442 patients were screened, of whom 535 (37%; 210 [39%] women and 325 [61%] men; mean age 57·9 years [SD 10·7]) were randomly assigned: 364 (68%) patients received renal artery denervation (mean age 57·9 years [10·4]) and 171 (32%) received the sham control (mean age 56·2 years [11·2]). 36-month follow-up data were available for 219 patients (original renal artery denervation group), 63 patients (crossover group), and 33 patients (non-crossover group). At 36 months, the change in office systolic blood pressure was -26·4 mm Hg (SD 25·9) in the renal artery denervation group and -5·7 mm Hg (24·4) in the sham control group (adjusted treatment difference -22·1 mm Hg [95% CI -27·2 to -17·0]; p≤0·0001). The change in 24 h ambulatory systolic blood pressure at 36 months was -15·6 mm Hg (SD 20·8) in the renal artery denervation group and -0·3 mm Hg (15·1) in the sham control group (adjusted treatment difference -16·5 mm Hg [95% CI -20·5 to -12·5]; p≤0·0001). Without imputation, the renal artery denervation group spent a significantly longer time in therapeutic blood pressure range (ie, better blood pressure control) than patients in the sham control group (18% [SD 25·0] for the renal artery denervation group vs 9% [SD 18·8] for the sham control group; p≤0·0001) despite a similar medication burden, with consistent and significant results with imputation. Rates of adverse events were similar across treatment groups, with no evidence of late-emerging complications from renal artery denervation. The rate of the composite safety endpoint to 48 months, including all-cause death, new-onset end-stage renal disease, significant embolic event resulting in end-organ damage, vascular complication, renal artery re-intervention, and hypertensive emergency was 15% (54 of 352 patients) for the renal artery denervation group, 14% (13 of 96 patients) for the crossover group, and 14% (10 of 69 patients) for the non-crossover group., Interpretation: This final report of the SYMPLICITY HTN-3 trial adds to the totality of evidence supporting the safety of renal artery denervation to 36 months after the procedure. From 12 months to 36 months after the procedure, patients who were originally randomly assigned to receive renal artery denervation had larger reductions in blood pressure and better blood pressure control compared with patients who received sham control., Funding: Medtronic., Competing Interests: Declaration of interests DLB served as the co-principal investigator of SYMPLICITY HTN-3 with funding from Medtronic paid to Brigham and Women's Hospital. DLB reports acting on advisory boards for AngioWave, Bayer, Boehringer Ingelheim, Cardax, CellProthera, Cereno Scientific, Elsevier Practice Update Cardiology, High Enroll, Janssen, Level Ex, McKinsey, Medscape Cardiology, Merck, MyoKardia, NirvaMed, Novo Nordisk, PhaseBio, PLx Pharma, Regado Biosciences, and Stasys; is a member of the Board of Directors of AngioWave (stock options), Boston VA Research Institute, Bristol Myers Squibb (stock), DRS.LINQ (stock options), High Enroll (stock), Society of Cardiovascular Patient Care, and TobeSoft; is the Inaugural Chair of the American Heart Association Quality Oversight Committee; has consulted for Broadview Ventures; is a member of Data Monitoring Committees for Acesion Pharma, Assistance Publique-Hôpitaux de Paris, Baim Institute for Clinical Research (formerly Harvard Clinical Research Institute, for the PORTICO trial, funded by St Jude Medical, now Abbott), Boston Scientific, Cleveland Clinic, Contego Medical, Duke Clinical Research Institute, Mayo Clinic, Mount Sinai School of Medicine, Novartis, and Population Health Research Institute; Rutgers University; honoraria from the American College of Cardiology, Arnold and Porter law firm (work related to Sanofi/Bristol-Myers Squibb clopidogrel litigation), and Baim Institute for Clinical Research (formerly Harvard Clinical Research Institute); is a member of the RE-DUAL PCI clinical trial steering committee funded by Boehringer Ingelheim; is a member of the AEGIS-II executive committee (funded by CSL Behring), Belvoir Publications, Canadian Medical and Surgical Knowledge Translation Research Group, Cowen and Company, Duke Clinical Research Institute, HMP Global, Journal of the American College of Cardiology, K2P, Level Ex, Medtelligence/ReachMD, MJH Life Sciences, Oakstone CME, Piper Sandler, Population Health Research Institute, Slack Publications, Society of Cardiovascular Patient Care, WebMD, and Wiley; is the deputy editor of Clinical Cardiology; the chair of NCDR-ACTION Registry Steering Committee, and VA CART Research and Publications Committee; holds a patent on sotagliflozin (patent application 17/574,977); is named on a patent for sotagliflozin assigned to Brigham and Women's Hospital who assigned to Lexicon (neither DLB nor Brigham and Women's Hospital receive any income from this patent); research funding from Abbott, Acesion Pharma, Afimmune, Aker Biomarine, Amarin, Amgen, AstraZeneca, Bayer, Beren, Boehringer Ingelheim, Boston Scientific, Bristol-Myers Squibb, Cardax, CellProthera, Cereno Scientific, Chiesi, CSL Behring, Eisai, Ethicon, Faraday Pharmaceuticals, Ferring Pharmaceuticals, Forest Laboratories, Fractyl, Garmin, HLS Therapeutics, Idorsia, Ironwood, Ischemix, Janssen, Javelin, Lexicon, Lilly, Medtronic, Merck, Moderna, MyoKardia, NirvaMed, Novartis, Novo Nordisk, Owkin, Pfizer, PhaseBio, PLx Pharma, Recardio, Regeneron, Reid Hoffman Foundation, Roche, Sanofi, Stasys, Synaptic, The Medicines Company, and 89Bio; reports royalties from Elsevier for Braunwald's Heart Disease; is a site co-investigator for Abbott, Biotronik, Boston Scientific, CSI, Endotronix, St Jude Medical (now Abbott), Philips, SpectraWAVE, Svelte, and Vascular Solutions; is a trustee of the American College of Cardiology; and reports unfunded research from FlowCo and Takeda. MV reports research grant support from or served on advisory boards for American Regent, Amgen, AstraZeneca, Bayer, Baxter Healthcare, Boehringer Ingelheim, Cytokinetics, Lexicon Pharmaceuticals, Novartis, Pharmacosmos, Relypsa, Roche Diagnostics, Sanofi, and Tricog Health; speaker engagements with AstraZeneca, Novartis, and Roche Diagnostics; and participates on clinical trial committees for studies sponsored by Galmed, Novartis, Bayer AG, Occlutech, and Impulse Dynamics. DEK reports institutional research or grant support from Medtronic and Ablative Solutions, and personal consulting honoraria from Medtronic. MBL reports institutional research support from Edwards Lifesciences, Medtronic, Boston Scientific, and Abbott; and has served on consulting or advisory boards for Medtronic, Boston Scientific, Gore, Meril Lifescience, and Abbott. SB, VD, and MF are employees of Medtronic. KR-S is a consultant for Alucent Biomedical. RRT reports grant support from the National Institutes of Health and consultant fees from Medtronic and JanssenMD; travel support from the American Society of Nephrology, North American Artery, and the National Kidney Foundation; and royalties from UpToDate. BTK is Chief Medical Executive and member of the steering committee for Medtronic Vascular. SO has received grant support from Medtronic, Merck, and Bayer; and personal fees from Medtronic, Daiichi Sankyo, and Bayer. GLB is supported by T32 National Institutes of Health grant DK07011 and is a consultant to Bayer, KBP Biosciences, Ionis, Alnylam, AstraZeneca, Quantum Genomics, Novo Nordisk, Dia Medica Therapeutics, and InREGEN; and is the Editor of the American Journal of Nephrology., (Copyright © 2022 Elsevier Ltd. All rights reserved.)