The health impact assessment (HIA) of urban air pollution conducted in the Bayonne metropolitan area is part of the Regional Air Quality Plan (PRQA). It follows the HIA methodology outlined by the French Institute for Public Health Surveillance (InVS). The pollution indicators selected are ozone (O3), nitrogen dioxide (NO2), and fine particulate matter (PM10). The health impact was assessed in the short term by estimating the number of premature deaths and hospital admissions attributable to pollution, and in the long term by estimating the annual number of deaths attributable to pollution. The selected study area consisted of 16 municipalities representing a total population of 148,742 inhabitants. The total number of premature deaths attributable in the short term to air pollution in the Bayonne metropolitan area for the year 2001 was estimated at 20 deaths. Calculations of health benefits associated with various air pollution reduction scenarios showed that a 25% reduction in the annual average O3 levels was the most effective scenario, yielding a health benefit of approximately 50% for both projected mortality and hospital admissions. Regarding long-term health impacts, a 5 μg/m³ reduction in the annual average PM10 level would prevent 32 deaths per year. Although the results must be interpreted with caution given the numerous uncertainties and limitations of the method used, this study highlights the significant health effects of urban air pollution in the Bayonne metropolitan area. The most effective measures would therefore be those that reduce not only the annual number of pollution peaks, but above all daily pollutant emissions. (R.A.)