OBJECTIVES: Biological valves are the most commonly implanted prostheses for aortic valve replacement (AVR) surgery in the UK. The aim of this study was to compare performance of porcine and bovine pericardial valves implanted in AVR surgery with respect to survival and reintervention-free survival in a retrospective observational study. METHODS: Prospectively collected clinical data for all first-time elective and urgent AVRs with or without concomitant coronary artery bypass graft (CABG) surgery performed in England and Wales between April 2003 and March 2013 were extracted from the National Institute for Cardiovascular Outcomes Research database. Patient life status was tracked from the Office for National Statistics. Time-to-event analyses were performed using log-rank tests and Cox proportional hazards regression modelling with random effects/grouped frailty for responsible cardiac surgeons. RESULTS: A total of 38,040 patients were included (64.9% bovine pericardial; 35.1% porcine). Patient characteristics were similar between the groups. The median follow-up was 3.6 years. There was no statistically significant difference in survival (P = 0.767) (the 10-year survival rates were 49.0 and 50.3% in the bovine pericardial and porcine groups, respectively) or reintervention-free survival. The adjusted hazard ratio for porcine valves was 0.98 (95% confidence interval 0.93-1.03). Sensitivity analysis in small valve sizes showed no difference in reintervention-free survival. After adjustment, there was some evidence of a protective effect for porcine valves in relatively younger patients (P = 0.075). CONCLUSIONS: There were no differences in reintervention-free survival between bovine pericardial and porcine valves used in first-time AVR ± CABG up to a maximum of 10 years.