We aimed to compare the clinical effectiveness, cost-effectiveness and complication rates of total ankle replacement with those of arthrodesis (i.e. ankle fusion) in the treatment of end-stage ankle osteoarthritis./r/nThis was a pragmatic, multicentre, parallel-group, non-blinded randomised controlled trial. Patients with end-stage ankle osteoarthritis who were aged 50-85 years and were suitable for both procedures were recruited from 17 UK hospitals and randomised using minimisation. The primary outcome was the change in the Manchester-Oxford Foot Questionnaire walking/standing domain scores between the preoperative baseline and 52 weeks post surgery./r/nBetween March 2015 and January 2019, 303 participants were randomised using a minimisation algorithm: 152 to total ankle replacement and 151 to ankle fusion. At 52 weeks, the mean (standard deviation) Manchester-Oxford Foot Questionnaire walking/standing domain score was 31.4 (30.4) in the total ankle replacement arm ( = 136) and 36.8 (30.6) in the ankle fusion arm ( = 140); the adjusted difference in the change was -5.6 (95% confidence interval -12.5 to 1.4; = 0.12) in the intention-to-treat analysis. By week 52, one patient in the total ankle replacement arm required revision. Rates of wound-healing issues (13.4% vs. 5.7%) and nerve injuries (4.2% vs. < 1%) were higher and the rate of thromboembolic events was lower (2.9% vs. 4.9%) in the total ankle replacement arm than in the ankle fusion arm. The bone non-union rate (based on plain radiographs) in the ankle fusion arm was 12.1%, but only 7.1% of patients had symptoms. A post hoc analysis of fixed-bearing total ankle replacement showed a statistically significant improvement over ankle fusion in Manchester-Oxford Foot Questionnaire walking/standing domain score (-11.1, 95% confidence interval -19.3 to -2.9; = 0.008). We estimate a 69% likelihood that total ankle replacement is cost-effective compared with ankle fusion at the National Institute for Health and Care Excellence’s cost-effectiveness threshold of £20,000 per quality-adjusted life-year gained over the patient’s lifetime./r/nThis initial report contains only 52-week data, which must therefore be interpreted with caution. In addition, the pragmatic nature of the study means that there was heterogeneity between surgical implants and techniques. The trial was run across 17 NHS centres to ensure that decision-making streams reflected the standard of care in the NHS as closely as possible./r/nBoth total ankle replacement and ankle fusion improved patients’ quality of life at 1 year, and both appear to be safe. When total ankle replacement was compared with ankle fusion overall, we were unable to show a statistically significant difference between the two arms in terms of our primary outcome measure. The total ankle replacement versus ankle arthrodesis (TARVA) trial is inconclusive in terms of superiority of total ankle replacement, as the 95% confidence interval for the adjusted treatment effect includes both a difference of zero and the minimal important difference of 12, but it can rule out the superiority of ankle fusion. A post hoc analysis comparing fixed-bearing total ankle replacement with ankle fusion showed a statistically significant improvement of total ankle replacement over ankle fusion in Manchester-Oxford Foot Questionnaire walking/standing domain score. Total ankle replacement appears to be cost-effective compared with ankle fusion at the National Institute for Health and Care Excellence’s cost-effectiveness threshold of £20,000 per quality-adjusted life-year gained over a patient’s lifetime based on long-term economic modelling./r/nWe recommend long-term follow-up of this important cohort, in particular radiological and clinical progress. We also recommend studies to explore the sensitivity of clinical scores to detect clinically important differences between arms when both have already achieved a significant improvement from baseline./r/nThis trial is registered as ISRCTN60672307 and ClinicalTrials.gov NCT02128555./r/nThis project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in ; Vol. 27, No. 5. See the NIHR Journals Library website for further project information.