Infection is an important arbiter of success or failure of surgical practice and the incidence of infection is incorporated into all surgical audit systems. If audit is to be of value the outcome end points of clinical practice must be defined. We have attempted to derive clinical definitions suitable for bedside diagnosis of infection and believe that these should bs supported by, but not be dependent upon, the results of laboratory or imaging techniques. The proposed definitions are intended to form the basis for clinical audit and to allow meaningful comparisons to be made on clear clinical criteria.