The systematic analysis of mortality among a population of workers in a particular industry or sector is a standard tool for the epidemiological surveillance of occupational risks. The observation of potential excess mortality for certain diseases, or the identification of disparities by occupation, industry sector, or occupational exposure, can help identify work-related health issues and assess their impact on the studied population. The study of mortality among current and former EDF-GDF workers over a 20-year period covered a population of approximately 180,000 men, among whom more than 15,000 deaths occurred. The analysis shows that, overall, they are characterized by a marked under-mortality compared to the general population, reflecting a better average state of health. Nevertheless, significant inequalities between occupational categories are observed within the company, with mortality rates being much higher among manual workers. Analyses of cancer data also reveal associations between mortality and exposure to certain chemicals used at the company. This initial report will be regularly followed by others, focusing on occupational populations of interest or sectors where health risks are known or suspected. (R.A.)