There is very little information available to document the role of occupational factors in the onset of diseases among the French population. Although a large number of diseases are caused (in part or in whole) by occupational activity, sufficient data—drawn from both the international literature and French sources—are available only for certain types of cancer. The study presented here seeks to estimate the proportion of certain cancers of occupational origin in France. This study was conducted within the framework of the commission established by Article L176-2 of the Social Security Code, tasked with assessing the proportion of occupational diseases in order to regulate the financial balances between branches of health insurance. Attributable fractions (AFs) were calculated for men in France in 1999, where data on lifetime exposure prevalence in the general population were available (asbestos, wood); otherwise, AFs derived from the international literature were applied. The calculations, performed under several assumptions, focused on lung cancer, pleural mesothelioma, bladder cancer, cancers of the nose and facial sinuses, and leukemias. Incidence data from 1995 published by FRANCIM and mortality data from 1999 published by CépiDC were used to estimate the number of cases attributable to occupational exposure among all cases occurring in the French male population. The number of cancers recognized as occupational diseases under the general social security system in 1999 was compared with these estimates. Occupational lung cancers likely number between 2,500 and 5,000 annually, with a proportion attributable to asbestos ranging from 10% to 14% of all such new cases, or 2,000 to 3,000 lung cancers. The number of bladder cancers attributable annually to occupational exposure among men in France is estimated at several hundred (600 to 1,000). Although the most conservative assumptions have generally been favored, the estimates obtained still show a clear undercompensation of work-related cancers. This is particularly evident for bladder cancers, for which fewer than 10 compensation cases were recorded under the General Social Security System in 1999. This situation likely stems largely from a significant underreporting of occupational diseases by the victims. Awareness of the occupational origin of these diseases, which most often occur while individuals are no longer working, remains very limited among general practitioners. (R.A.)