Surgical wound infection is an important outcome indicator in the postoperative period. A 3-year prospective cohort epidemiological study of 2202 surgical patients from seven surgical wards, across two hospitals, was carried out using gold standard surveillance methodology. This involved following patients up as inpatients and postdischarge surveillance to 30 days by an independent observer. The results led to the development of a mathematical model for risk of clean, elective surgical wound infection. Risk of surgical wound infection was increased by smoking, higher body mass index, presence of malignancy, haematoma formation, increasing numbers of people in theatre, adherent dressing usage, and higher times to suture removal (P<0.05). The results show that this type of surveillance is an effective way of collecting accurate data on wound infection rates. It was noted that patient care practices affected the surgical wound infection rate and the surveillance was used to facilitate the adoption of evidence-based practice, through recommendations for clean surgery, to reduce the risk from extrinsic risk factors for wound infection. As a result of the implementation of this evidence-based practice there was a significant reduction (P<0.05) in the clean wound infection rate.