More than twice as many workdays are lost to illness than for personal or family reasons. We examine possible workplace determinants of sickness absence among French workers in the food processing industry. These workers are exposed to a variety of environmental and organizational constraints: cold, uncomfortable postures, assembly-line work, and irregular schedules. In 1987-1988, a medical examination and questionnaire were administered to 558 men and 790 women as part of a study of 17 poultry slaughterhouses and 6 canning factories. Women's and men's working conditions were very different, and their sickness absences for musculoskeletal and respiratory illnesses were related to some of their specific working conditions: cold exposure, ill-adapted work stations, and problems with their supervisors and co-workers. If male and female workers were combined into a single analysis that adjusted for sex, many of the associations operant for a single sex could no longer be seen.