Daily counts of non-accidental deaths in Santiago, Chile, from 1988 to 1996 were regressed on six air pollutantsfine particles (PM 2.5 ), coarse particles (PM 10-2.5 ), CO, SO 2 , NO 2 , and O 3 . Controlling for seasonal and meteorological conditions was done using three different modelsa generalized linear model, a generalized additive model, and a generalized additive model on previously filtered data. Single-and two-pollutant models were tested for lags of 1-5 days and the average of the previous 2-5 days.The increase in mortality associated with the mean levels of air pollution varied from 4 to 11%, depending on the pollutants and the way season of the year was considered. The results were not sensitive to the modeling approaches, but different effects for warmer and colder months were found. Fine particles were more important than coarse particles in the whole year and in winter, but not in summer. NO 2 and CO were also significantly associated with daily mortality, as was O 3 in the warmer months. No consistent effect was observed for SO 2 . Given particle composition in Santiago, these results suggest that combustion-generated pollutants, especially from motor vehicles, may be associated with increased mortality. Temperature was closely associated with mortality. High temperatures led to deaths on the same day, while low temperatures lead to deaths from 1 to 4 days later. IMPLICATIONSSignificant statistical associations were found between daily mortality in Santiago for 1988-1996 and several measures of ambient air pollution (PM 2.5 , PM 10-2.5 , CO, NO 2 , and O 3 ). The risks for PM 2.5 , NO 2 , and CO were comparable. PM 10-2.5 and O 3 were significant only during the warmer months. SO 2 did not show a consistent statistically significant risk. The results suggest that combustion sources may be responsible for increased mortality in Santiago.