OBJECTIVES: To determine the cost-effectiveness of Transcatheter aortic valve implantation (TAVI) compared to surgical aortic valve replacement (SAVR) in a high-risk aortic stenosis (AS) population from the perspective of the UK health and personal social services. METHODS: A Markov model was developed to enable a cost-utility analysis employing NICE reference case methods.  A systematic review was conducted to identify model parameter values. Mean utility values per NYHA category were derived from a UK high-risk AS population. Two-year TAVI and SAVR effectiveness was taken from the PARTNER A trial. Costs and effects were modelled from two years over a 10 year horizon via NYHA health state transitions. Incremental cost-effectiveness ratios (ICER) and cost effectiveness acceptability curves (CEAC) were calculated and deterministic and probabilistic sensitivity analyses conducted. RESULTS: Despite greater procedural costs (£16,500 vs. £9,256), TAVI was cost-effective compared to SAVR over 10 years (costs £52,593 vs. £53,943 and QALYs 2.81 vs 2.75), indicating TAVI dominated SAVR. This appeared to be due to greater SAVR post-surgical costs and attendant length and cost of hospital stay. The results appeared robust to a number of deterministic sensitivity (including high stroke rates, worst case scenario complication rates, alternative utility values and higher costs) and probabilistic analyses. Given modest cost savings and QALY benefits conferred by TAVI, results were sensitive to some parameter changes when incurred by one arm in isolation. The CEAC indicated that at a £20,000 incremental QALY willingness to pay threshold, TAVI had a 64.6% likelihood of being cost-effective. CONCLUSIONS: This economic evaluation is the first to incorporate two year data comparing TAVI and SAVR in elderly high risk AS patients. TAVI is likely to be a cost-effective option compared to SAVR. However, uncertainty surrounding the long-term outcomes for TAVI patients remains; this could have a substantive impact on estimates of cost-effectiveness.