Accurate information on the prevalence of surgical wound infection is difficult to obtain; outpatient follow-up is often inadequate. For two months in 1993 and again in 1995, surgical wounds throughout one hospital were examined by the same observer with the intention of comparing different methods for assessing wound infection. Two standard definitions [Centers for Disease Control (CDC), USA and National Prevalence Survey (NPS), UK] were compared with ASEPSIS and the Southampton method. In 1993, 325 wounds in 230 patients were examined with follow-up of 203 (88%) patients. In 1995, 559 wounds were surveyed in 375 patients with follow-up in 364 (97%). Patient groups in the two years were similar. ASEPSIS identified 92 (13%) wounds as having scored over 20 points indicating infection, and another 16.5% having disturbance of healing. There was no significant difference between the two surveys. The two scoring methods were more sensitive than the standard definitions but CDC and NPS did not differ significantly from each other. Between 44 and 47% of clean wounds identified as infected by standard definitions were classed as disturbance of healing by ASEPSIS. All methods were labour-intensive and to implement any one of them on a regular basis would require a full-time investigator. The first surveillance program with feedback of results to the surgeons did not significantly affect the rates two years later.