BACKGROUND: The potential severity of wrong patient/procedure/site of surgery and the view that these events are avoidable, make the prevention of such errors a priority. An intervention was set up to develop a verification protocol for checking patient identity and the site of surgery with periodic audits to measure compliance while providing feedback. ASSESSMENT OF PROBLEM: A nurse auditor performed the compliance audits in inpatients and outpatients during three consecutive 3-month periods and three 1-month follow-up periods; 11 audit criteria were recorded, as well as reasons for not performing a check. STRATEGY FOR CHANGE: The nurse auditor provided feedback to the health professionals, including discussion of inadequate checks. RESULTS: 1,000 interactions between patients and their anaesthetist or nurse anaesthetist were observed. Between the first and second audit periods compliance with all audit criteria except "surgical site marked" noticeably improved, such as the proportion of patients whose identities were checked (62.6% to 81.4%); full compliance with protocol in patient identity checks (9.7% to 38.1%); proportion of site of surgery checks carried out (77.1% to 92.6%); and full compliance with protocol in site of surgery checks (32.2% to 52.0%). Thereafter, compliance was stable for most criteria. The reason for failure to perform checks of patient identity or site of surgery was mostly that the anaesthetist in charge had seen the patient at the preanaesthetic consultation. LESSONS AND MESSAGES: By combining the implementation of a verification protocol with periodic audits with feedback, the intervention changed practice and increased compliance with patient identity and site of surgery checks. The impact of the intervention was limited by communication problems between patients and professionals, and lack of collaboration with surgical services.