The GAZEL Cohort Study was set up in 1989 among Électricité de France-Gaz de France (EDF-GDF) workers. It is an open epidemiologic laboratory characterized by a broad coverage of health problems and determinants and accessible to the community of researchers. At inception in 1989, the GAZEL Cohort Study included 20 625 volunteers working at EDF-GDF then aged from 35 to 50 years (15 011 men and 5614 women). The cohort is broadly diverse in terms of social, economic, and occupational status, health, and health-related behavior. The data collected routinely cover diverse dimensions and come from different sources: annual self-administered questionnaire (morbidity, lifestyles, life events, etc.); personnel department of EDF-GDF for social, demographic, and occupational characteristics; EDF-GDF special social insurance fund (for sickness absences and cancer and ischemic heart disease registries), occupational medicine (occupational exposure and working conditions), Social Action Fund (healthcare utilization), Health Screening Centers for standardized health examination and the constitution of a biobank, and the National Death Register (causes of death). Follow-up has been excellent, and the number of subjects lost to follow-up was exceptionally low; active participation by the self-administered questionnaire is also elevated. Today, more than 40 projects on diversified themes have been set up in the GAZEL Cohort Study by some 30 French and foreign teams. Different health problems taking into account behavioral, social, psychological and medical occupational risk factors have been the object of research projects in the cohort. A substantial proportion of the research work has focused on social inequalities in health. Here, we present a brief panorama of the main fields covered by research in the GAZEL Cohort Study that have already been published over the years.