Surveillance is a primary component of systems for the prevention of health care-associated infections (HCAI). Feedback to surgeons from these surveillance systems may reduce rates of surgical site infections (SSIs) by approximately 20%. Our objective was to describe the Norwegian Surveillance System for Healthcare-Associated Infections' (NOIS) module for SSI (NOIS-SSI) and to evaluate the completeness of hospital participation, the effectiveness of automated data collection, and the added value of follow-up after hospital discharge during 2005 to2009. NOIS was introduced by regulation in 2005. Hospital participation is described through adherence to the mandatory requirements and participation in the voluntary aspects of the system. Automated data collection is evaluated through the completeness of reporting of explanatory and administrative variables. The impact of active postdischarge surveillance is assessed through the completeness of follow-up and the proportion of infections detected after hospital discharge. The system has achieved 95% (52/55) hospital participation, with 65% (34/52) of the hospitals submitting more data than the required minimum. The completeness of patient and procedure-related background data is satisfactory, with 23.3% (5,079/21,772) of the records having at least 1 missing value. The completeness of 30-day follow-up of patients is 90.7% (19,747/21,772), and 81% (765/948) of the infections were detected after discharge from hospital. Implementation of a new surveillance system for SSI has been successful evaluated through hospital participation, the completeness of reporting of explanatory and administrative variables, and the completeness of postdischarge follow-up. Important success factors are a mandatory system, automated data-harvesting systems in hospitals, and active postdischarge surveillance.