Recently new European policies on ambient air quality--namely, the adoption of new standards for fine particulate matter (PM(2.5)), have generated a broad debate about choosing the air quality standards that can best protect public health. The Apheis network estimated the number of potential premature deaths from all causes that could be prevented by reducing PM(2.5) annual levels to 25 microg/m3, 20 microg/m3, 15 microg/m3 and 10 microg/m3 in 26 European cities. The various PM(2.5) concentrations were chosen as different reductions based on the limit values proposed by the new European Directive, the European Parliament, the US Environmental Protection Agency and the World Health Organization, respectively. The Apheis network provided the health and exposure data used in this study. The concentration-response function (CRF) was derived from the paper by Pope et al (2002). If no direct PM(2.5 )measurements were available, then the PM(10) measurements were converted to PM(2.5 )using a local or an assumed European conversion factor. We performed a sensitivity analysis using assumptions for two key factors--namely, CRF and the conversion factor for PM(2.5). Specifically, using the "at least" approach, in the 26 Apheis cities with more than 40 million inhabitants, reducing annual mean levels of PM(2.5) to 15 microg/m3 could lead to a reduction in the total burden of mortality among people aged 30 years and over that would be four times greater than the reduction in mortality that could be achieved by reducing PM(2.5) levels to 25 microg/m3 (1.6% vs 0.4% reduction) and two times greater than a reduction to 20 microg/m3. The percentage reduction could grow by more than seven times if PM(2.5) levels were reduced to 10 microg/m3 (3.0% vs 0.4%). This study shows that more stringent standards need to be adopted in Europe to protect public health, as proposed by the scientific community and the World Health Organization.