The purpose of this article is to describe the role of surveillance in the policy for combating healthcare-associated infections at the Mulhouse Hospital Center. Initially organized by the microbiology laboratory, the surveillance program subsequently expanded to include a two-pronged approach: epidemiological monitoring and public health surveillance. Epidemiological monitoring includes network-based surveillance following a national methodology, as well as surveillance based on data from the microbiology laboratory and the pharmacy in the following areas: control of infection risk in operating rooms and intensive care units; control of the spread of multidrug-resistant (MDR) bacteria; and control of healthcare-associated infections linked to medical devices and those observed among healthcare professionals. Health surveillance encompasses the internal reporting of adverse events involving infection risk. Surveillance of surgical site infections based on sentinel procedures is in place for all surgical specialties. This has enabled two of these specialties to develop a prevention program in collaboration with the Committee for the Control of Nosocomial Infections and to monitor its effectiveness. Surveillance of healthcare-associated infections (HAIs) is based on an organizational structure in which the hospital hygiene operational team actively engages with clinical departments. This policy contributed to controlling the regional outbreak of glycopeptide-resistant enterococci in eastern France. The surveillance results have made it possible to set priorities for the infection control program and track trends. They shed light on current risks and allow the facility to adapt its prevention policy to emerging trends. Surveillance becomes the foundation for pragmatic actions. (R.A.)