Objectives - In 2003, the surveillance system for notifiable diseases underwent significant changes, with enhanced protection of individual anonymity, to facilitate the introduction of new mandatory reporting requirements that particularly involved laboratory technicians. Methods - In 2005, an assessment of potential reporters’ knowledge and attitudes toward MDOs, as well as an evaluation of reporting practices, was conducted via telephone interviews. Two representative samples of 400 physicians from eight medical specialties and 400 biologists were randomly selected using a stratified random sampling method. Results - Among biologists, 78% were familiar with at least two of 26 ADEs, and 42% had reported at least one since 2003. Among physicians, 77% could name two ADEs, and 23% had submitted at least one report. Among biologists and physicians who were familiar with two ADEs but had never reported them, half had diagnosed at least one. Barriers to reporting are primarily linked to a lack of understanding of their role and the reporting process. Among those who report, the system is generally well accepted. However, one-quarter of biologists and 38% of reporting physicians believe the procedure is too bureaucratic and time-consuming. Better information, targeted feedback, and digitization of the process are among the desired improvements. Conclusion - Adverse event reporting is well accepted by those who practice it. The main barriers to reporting remain a lack of understanding of the system and the roles of the various stakeholders in the process. Adverse event reporting remains an administrative and complex process for some reporters. Efforts to raise awareness among stakeholders and improvements to the system are necessary. (R.A.)