In France, the recognition of the occupational nature of diseases is based primarily on the presumption of occupational origin and relies on the existence of schedules of compensable occupational diseases (MPI). Occupational diseases (MCP) are, in theory, all diseases that may be work-related but do not fall under the MPI lists. Although reporting them is a legal obligation for all medical doctors, few physicians report MCPs. Furthermore, these reports are rarely utilized, particularly due to a lack of data on the population from which they originate. The surveillance network for musculoskeletal disorders (MSDs) established in 2002 in the Pays de la Loire region includes, among its objectives, exploring the use of ODD reports for epidemiological surveillance in the workplace. A comprehensive data collection effort, conducted over a single week repeated during a pilot phase spanning three semesters and based on a network of volunteer occupational physicians, was launched in 2003 across the region’s five departments. Physicians submit reports of MCP cases they have identified during occupational health visits during these weeks, dubbed "MCP Weeks," to the Occupational Health Inspection, along with the age, gender, and industry sector of all employees who underwent a medical examination during the same period. Nearly half of the region’s occupational physicians participated in this pilot phase. The region’s sectors of activity were generally well represented. For 23,416 employees seen in consultation, 1,056 reports were filed. MSDs accounted for 65% of these conditions. The observed prevalence of MSDs was 2.9%. The sectors with the highest rates were identified. According to the occupational physician, MSDs were part of an occupational disease profile in 61% of cases. These three weeks provided an opportunity for significantly improved reporting. If repeated regularly, these efforts will provide unprecedented data on the frequency of work-related health conditions, as well as valuable insight into the extent of underreporting of conditions eligible for reporting under the MPI categories. This surveillance is currently being expanded to other regions. (R.A.)