OBJECTIVES: To estimate the health and economic benefits that would result from two scenarios of improved air quality in 57 municipalities of the metropolitan area of Barcelona. METHODS: We used attributable fractions and life tables to quantify the benefits for selected health outcomes, based on published concentration-response functions and economic unit values. The mean weighted concentration of PM(10) for the study population was estimated through concentration surface maps developed by the local government. RESULTS: The annual mean health benefits of reducing the mean PM(10) exposure estimated for the population in the study area (50microg/m(3)) to the annual mean value recommended by the World Health Organization (20microg/m(3)) were estimated to be 3,500 fewer deaths (representing an average increase in life expectancy of 14 months), 1,800 fewer hospitalizations for cardio-respiratory diseases, 5,100 fewer cases of chronic bronchitis among adults, 31,100 fewer cases of acute bronchitis among children, and 54,000 fewer asthma attacks among children and adults. The mean total monetary benefits were estimated to be 6,400 million euros per year. Reducing PM(10) to comply with the current European Union regulatory annual mean level (40microg/m(3)) would yield approximately one third of these benefits. CONCLUSIONS: This study shows that reducing air pollution in the metropolitan area of Barcelona would result in substantial health and economic benefits. The benefits are probably underestimated due to the assumptions made in this study. Assessment of the health impact of local air pollution is a useful tool in public health