AIMS: Lifestyle risk factors are thought to increase the risk of infection after acute orthopaedic surgery but the evidence is scarce. We aimed to investigate whether smoking, obesity and alcohol overuse are risk factors for the development of infections after surgery for a fracture of the ankle.PATIENTS AND METHODS: We retrospectively reviewed all patients who underwent internal fixation of a fracture of the ankle between 2008 and 2013. The primary outcome was the rate of deep infection and the secondary outcome was any surgical site infection (SSI). Associations with the risk factors and possible confounding variables were analysed univariably and multivariably with backwards elimination.RESULTS: A total of 1043 patients were included; 64 (6.1%) had a deep infection and 146 (14.0%) had SSI. Obesity was strongly associated with both outcomes (odds ratio (OR) 2.21, p = 0.017 and OR 1.68, p = 0.032) in all analyses. Alcohol overuse was similarly associated, though significant only in unadjusted analyses. Surprisingly, smoking did not yield statistically significant associations with infections.CONCLUSION: These findings suggest that obesity and possibly alcohol overuse are independent risk factors for the development of infection following surgery for a fracture of the ankle. This large study brings new evidence concerning these common risk factors; although prospective studies are needed to confirm causality. Cite this article: Bone Joint J 2017;99-B:225-30.