Objective - To assess the understanding, perception, and impact of the Composite Index of Activities to Combat Nosocomial Infections (Icalin) among healthcare professionals, patients, and healthcare facility users. Methods - A questionnaire survey was conducted among randomly selected healthcare professionals, physicians, nurses, and healthcare managers, as well as patients and visitors selected by admission specialty, gender, and age group in 18 healthcare facilities in Upper Normandy. Results - 293 healthcare professionals, 133 hospitalized patients, 157 discharged patients, and 91 patient visitors participated; 86% of healthcare professionals and 61% of patients knew that the Icalin does not provide information on the frequency of infections; the index was understood by healthcare professionals and patients, but the categories were misinterpreted by patients; 39% of healthcare professionals reported changing their practices based on the Icalin, 30% believed that publishing the Icalin would encourage infected patients to file complaints, and 70% believed that the Icalin would influence patients’ choice of healthcare facility; 78% of patients considered it important to know a facility’s Icalin score, but ranked it only 6th out of 7 factors influencing their choice; 57% would consult their doctor’s opinion if faced with a low Icalin score. Conclusion - The Icalin appears to be viewed favorably by patients, users, and professionals. The actual impact of disseminating this index on attitudes and practices remains to be assessed. (R.A.)