About 1,000,000 hospital days attributable to surgical site infections can be expected per year in German hospitals. Among the various measures for prevention, surveillance of surgical site infections is strongly recommended. Therefore, beginning in 1997 the National Reference Center for Surveillance of Nosocomial Infections began to establish a hospital infection surveillance system in order to provide data for prevention and control of these infections. The surveillance system (called KISS) documents postoperative surgical site infections in patients undergoing selected indicator procedures. Today we have an overview of 274,050 procedures for a total of 20 operative indicator procedures. A further surveillance component focussing on surgical site infections in outpatient settings has recently been developed (AMBU-KISS). The participating hospitals and outpatient settings regularly receive their infection rates as well as the equivalent data of all hospitals involved in order to assess the position of their own hospital. However, competent and meaningful interpretation of these data is necessary for internal quality management in order to avoid wrong conclusions. The available results demonstrate that this approach can lead to a substantial reduction of surgical site infections.