Exposures to air pollution in developed countries have generally decreased over the last two decades. However, many recent epidemiological studies have consistently shown positive associations between low-level exposure to air pollutants and health outcomes. In Portugal, very few studies have analysed the acute effect of air pollutants on health.The present study evaluates the association between exposure to air pollution and daily mortality in the Oporto Metropolitan Area, Portugal. Generalised additive models were used for this analysis. Pollutants assessed were ozone, nitrogen dioxide, and particulate matter (PM10). Models were adjusted for time trend, seasonality, and weather.We report that an increase of 10γg/m3 in the daily ozone 8-h maximum moving-average corresponds to an increase of 0.95% (95%CI: 0.30, 1.60) and 1.58% (95%CI: 0.45, 2.73) in non-accidental mortality and cardiovascular mortality, respectively, in the summer season. A significant effect of 0.67% (95% CI: 0.03:1.32) was also found for the association between PM10 and non-accidental mortality in the summer season. Associations with ozone and PM10 exposures were higher in the elderly people. No significant effects on mortality were observed during the summer season with nitrogen dioxide exposures.Our analyses provide the first significant evidence in Oporto that exposures to O3 and PM10 have adverse effects on the health of the general population in the summer months.