Introduction - Musculoskeletal disorders (MSDs) are the leading occupational disease (OD) compensated by the general Social Security system. Statistics from the occupational disease compensation system are regularly criticized due to underreporting, which has been little studied to date. The objective of this study was to estimate the underreporting of MSDs affecting the shoulder, hand-wrist-fingers, and lumbar spine. Materials and Methods - This study drew on MSDs recognized as occupational diseases under the general Social Security system and those reported as work-related conditions (WRCs) by a network of volunteer occupational physicians in seven French regions in 2007. An indicator approximating the underreporting rate was constructed and analyzed by sex, age, and sector of activity. Results The underreporting indicator was 68% (range 63–72) for MSDs of the hand, wrist, and fingers; 74% (range 69–78) for those of the shoulder; and 80% (range 72–89) for the lumbar spine. It tended to decrease with age for the shoulder and varied little across sectors of activity. Discussion-conclusion - This indicator provides a method for measuring the extent of underreporting. The higher underreporting of spinal conditions could be linked to the fact that the balance between benefits (medical and social) and risks (to employment) is less favorable than for other body regions. The results also show that underreporting is a widespread phenomenon regardless of industry sector. (R.A.)