The health impact assessment (HIA) of air pollution in the Valence metropolitan area is part of the Rhône-Alpes Region’s Regional Air Quality Plan (PRQA), which sets out guidelines aimed at preventing, reducing, or mitigating the effects of air pollution. In this study, the short-term health impact of air pollution is calculated in terms of premature mortality and morbidity (hospital admissions). The long-term health impact is estimated by the number of deaths attributable to air pollution. The selected study area corresponds to an urban zone where the population’s exposure to air pollution can be considered homogeneous. It comprises four municipalities: Valence, Portes-les-Valence, Bourg-les-Valence in the Drôme department, and Guilherand-Granges in the Ardèche department, representing a total population of 101,350 inhabitants. The study period spans two winter seasons: January 1, 2001, to December 31, 2001, for mortality data, and January 1, 2002, to December 31, 2002, for morbidity data (hospital admissions). The winter season is reconstructed based on two periods: January 1 through March 31 and October 1 through December 31. This study is based on the urban air pollution EIS methodology proposed by the French Institute for Public Health Surveillance (InVS), which consists of four steps: hazard identification, selection of exposure-risk relationships, exposure estimation, and risk characterization. The air pollution indicators selected are based on the four pollutants routinely measured in the area: SO₂, NO₂, O₃, and PM10. The exposure-risk relationships used are derived from epidemiological studies conducted in the general population, with a focus on multicenter and European studies. The annual short-term health impact of air pollution amounts to 20 [14–26] premature deaths, 4 [2–7] hospital admissions for respiratory reasons among those aged 65 and older, 25 [15–36] hospital admissions for cardiovascular reasons in winter, and 15 [19–22] in summer. Various air pollution reduction scenarios show that the greatest health gains are achieved with a 25% reduction in average annual pollution levels. The long-term health impact of air pollution amounts to 21 [13–30] annual deaths. Only a reduction in pollution levels would lead to a health benefit: a 25% reduction in annual average levels would be associated with a 62% health benefit. Given the uncertainties and limitations of the methodology used, the results should be interpreted as orders of magnitude of the impact of air pollution on the health of the population in the study area. Air pollution is responsible for health effects far broader than those explored in the study; it is also responsible in the short term for an increase in respiratory diseases, particularly among asthmatics, and in the long term for a lasting decline in respiratory function. However, this study shows that even if the relative risks associated with air pollution are low, the large proportion of people exposed results in a significant collective impact. It also shows that health effects are already evident at pollution levels well below those for which measures are currently taken, and that the most effective actions would therefore be those that combine daily reductions in emissions at the source with a significant decrease in the number of annual pollution peaks. (R.A.)