This study evaluated the costs of work-related stress in France. Three illnesses--cardiovascular diseases, depression, musculoskeletal diseases and back pain--that may result from exposure to stress are identified and the proportions of cases attributable to the risk factor are calculated from epidemiological studies. Two methodological hypotheses allow us to provide complementary evaluations of the social cost of occupational stress and raise the ethical questions inherent in the choice of methodology. For the year 2000 our model shows that of a working population of 23.53 million in France some 310,000-393,400 persons (1.3-1.7%) were affected by illnesses attributable to work-related stress, and that 2,300-3,600 persons died as a result of their illness. Work-related stress costs society between Euro 1,167 million and Euro 1,975 million in France, or 14.4-24.2% of the total spending of social security occupational illnesses and work injuries branch.