Objective. In France, the recognition of occupational diseases is based primarily on the presumption of occupational origin and relies on the existence of lists of compensable occupational diseases (MPI) that include medical, technical, and administrative criteria. Occupational diseases (MCP) are, in theory, all diseases that may be of occupational origin but do not fall under the MPI schedules or the complementary compensation system (Regional Committees for the Recognition of Occupational Diseases). 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 medico-social component of the musculoskeletal disorders (MSDs) surveillance network established in 2002 by the French Institute for Public Health Surveillance (InVS) in the Pays de la Loire region has, among its objectives, to explore the use of MCP reports for epidemiological surveillance in the workplace, notably by enabling the estimation of the prevalence of these work-related pathological conditions and the assessment of the extent of underreporting of diseases that could be reported under occupational diseases. Method. A registry designed to be comprehensive over a repeated one-week period, in a pilot phase spanning three semesters, and based on a network of volunteer occupational physicians, was established in 2003 in the region’s five departments. Physicians submit reports of work-related musculoskeletal disorders (WMSDs) they identified during occupational health visits during these weeks—dubbed WMSD Weeks—to the Occupational Health Inspection, along with the age, sex, and industry sector of all employees who underwent a medical examination during the same period. Results. Nearly half of the region’s occupational physicians participated in this pilot phase. The 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, followed by mental health issues (24%), skin diseases (5%), ear disorders (2.5%), and respiratory diseases (2%). The observed prevalence of MSDs was 2.9%. The sectors with the highest rates were identified. According to the occupational physician, MSDs were classified as work-related in 61% of cases. In 43% of cases, the lack of a work-related classification was due to the employee’s refusal. Conclusion. These three weeks provided an opportunity for improved reporting: over 1,000 reports versus 845 in 2001 and 536 in 2002 for the entire year and all physicians in the region. If repeated regularly, these reports will provide unprecedented data on the frequency of work-related health conditions, as well as a valuable estimate of the extent of underreporting of conditions eligible for reporting under the occupational disease categories. This surveillance, coordinated by the French Institute for Public Health Surveillance, is currently being expanded to other regions, with the ultimate goal of establishing a national surveillance system.