One prospective observational study using logistic regression to analyse data collected from 142 medical centres identified age as an independent risk factor for SSI. [EL = 2+] Trained nurses gathered data on inherent and operative risk factors for SSI in patients undergoing general and vascular surgery. Of 163 624 patients who were included in the study, 7035 developed SSI within 30 days of surgery. Patients aged over 40 had a statistically significantly increased risk of developing SSI compared with those under 40 years (OR 1.24, 95% CI 1.07 to 1.44).