The epidemiological surveillance program in nine major French cities (PSAS-9) aims to assess the relationship between exposure to urban air pollution and indicators of population health in order to evaluate the impact of pollution on residents’ health. Following a standardized protocol, the 9 urban areas collected aggregated daily pollution indicators from a network of monitoring stations and aggregated mortality indicators from death registries. These data were analyzed using time-series modeling methods. The estimated short-term excess risk for all-cause mortality ranged from 1.2% to 1.9%, depending on the exposure indicator. The potential annual health benefit associated with a 50% reduction in average pollution levels was estimated at 2,786 deaths across the nine cities. (R.A.)