While the value of the Hospital-Acquired Infection Reporting System (SIN) in terms of patient safety has been demonstrated, several evaluations have shown that its operation was not optimal. A qualitative evaluation was therefore conducted in 2009 to better understand the dynamics of the SIN in healthcare facilities (HFs). It was based on observations and semi-structured interviews with healthcare professionals from 12 HFs in the West and Southwest regions and with several national experts. The study highlighted varied reporting dynamics, organized around the chair of the Committee for the Control of Nosocomial Infections (Clin) and the Operational Hygiene Teams (EOH) but poorly integrated into risk management. The barriers to external reporting (ER) were primarily those of internal reporting (IR) to the EOH: debate over the nosocomial nature of the infection, low involvement of clinicians or paramedical staff, a negative perception of the system, or dissatisfaction among certain EOHs. The ER system was considered difficult to understand and lacking in appropriate tools. Conversely, several factors appeared to facilitate good reporting practices: the presence of motivated professionals, the proximity of EOHs to clinical departments, the automation of alerts within healthcare facilities, or acceptance of quality initiatives. The study suggests avenues for improvement: increasing the system’s clarity by clarifying its objectives and workflows, adapting its implementation to on-the-ground realities, refining the definition of nosocomial infection, strengthening training for healthcare facilities, and developing forums for professional exchange. The implementation of formalized feedback mechanisms (REX) and the digitization of reporting (e-SIN) are steps in this direction. (R.A.)