The development of tools to assess occupational exposures is necessary to improve understanding and monitoring of occupational risks. The Occupational Health Department of the French Institute for Public Health Surveillance has established and coordinates a program to develop job-exposure matrices tailored to the general French population (the Matgéné program).An occupation-exposure matrix can be briefly described as a table showing the correspondence between job titles and exposure indices for one or more hazards. When these matrices are cross-referenced with individual occupational histories, exposures are automatically assigned to individuals based on their job titles. These matrices have numerous potential applications in the field of occupational health surveillance and research. For example, they can be used to estimate the prevalence of occupational exposures in the population and study their distribution and trends, to assess occupational exposures of subjects in epidemiological studies, or as an aid in identifying exposures for prevention or medical-social management. The matrices developed are specific to a substance or group of substances. With a view to generalizability, each matrix comprehensively covers all exposed occupations and industries, along with the corresponding codes in several classification systems. The creation of each matrix is accompanied by the development of a technical document summarizing the characteristics of the hazard under study, its health effects, relevant regulations, and exposure circumstances. This document outlines the methodology used to develop the matrices and the program’s current status. By way of illustration, two job-exposure matrices (flour dust and leather dust) are then presented in detail, with application examples for each. (R.A.)