Surgical site infections (SSI) are significant postoperative complications and a leading cause of healthcare-associated infections (HAI) worldwide. They are associated with excess morbidity and mortality, and lead to decreased quality of life, prolonged hospital length of stay, and increased costs. Surveillance of HAI, including SSI, is a cornerstone of effective infection prevention and control (IPC) programmes. Surveillance activities can guide the implementation, and assess the effectiveness of preventive programmes aimed at reducing SSI incidence. In this Privat-Docent thesis we include four publications that contribute a unique perspective to SSI surveillance. The first publication addresses the intrinsic effect of surveillance. We performed a large international cohort study of SSI surveillance networks in 15 countries, and were able to determine that a hospital’s duration of participation in a surveillance network was associated with a decrease in its SSI incidence. This study confirms the existence of the “surveillance effect”, implying that awareness and monitoring can drive improvements in clinical practice and outcomes. The second publication examines the temporal trends and epidemiology of SSI due to Staphylococcus aureus in Switzerland, using data from the Swiss SSI surveillance network (Swissnoso), and showed that there were decreasing trends in incidence. We also examined risk factors associated with both methicillin-susceptible and methicillin-resistant S. aureus, helping to inform targeted prevention approaches, and to identify high-risk populations for further studies. The third publication used data from SSI surveillance networks in England, France, and Switzerland to externally validate risk predictions scores for SSI in colorectal surgery, where the burden is the highest, and to develop a novel score. The study highlighted the limitations of current models and underscores the need for more accurate prediction tools, which rely on data that is beyond what is routinely collected for the purposes of surveillance. The fourth publication charts a strategic roadmap, developed by a multidisciplinary group of European experts in surveillance, for the transition to automated HAI surveillance across Europe, including SSI. It emphasises benefits for surveillance practices that are brought about by digitalisation and automation in terms of efficiency and standardization, but also discusses common challenges and key questions such as surveillance targets. It is intended to accompany individuals or institutions that wish to implement an automated HAI surveillance programme.