Introduction. Healthcare-associated adverse events (AEs) are underreported, and the barriers to reporting them remain poorly understood. The objective of this study was to identify the barriers to reporting healthcare-associated AEs. Materials and Methods. A descriptive cross-sectional study was conducted using a standardized self-administered questionnaire between January and June 2010 among all medical and paramedical staff at the Édouard Herriot Hospital Group (Lyon University Hospital). The items included scenarios for reporting and sought to identify reasons for non-reporting. Results. A total of 415 healthcare workers from 24 clinical departments were included, of whom 62% (n=255) reported knowing the definition of an adverse event. The main reasons cited for not reporting adverse events were lack of knowledge of the reporting system (n=342; 82%), a lack of perceived value in reporting (n=243; 58%), an excessive workload (n=161; 39%), and fear of sanctions (n=103; 25%). Discussion and Conclusion. Healthcare providers generally had a good understanding of the concepts of adverse events and reporting. Lack of familiarity with the system and a lack of feedback were the main barriers to reporting adverse events. Strengthening adverse event reporting systems must be achieved through continuing education and information for healthcare providers. (R.A.)