OBJECTIVES: To examine the relationship between air pollution exposure and mortality in Seoul for the years of 1991-1995. METHODS: Daily counts of death were analyzed by general additive Poisson model, with adjustment for effects of secular trend, seasonal factor, day of the week, heat wave, temperature, and humidity. Pollution variables were ozone, nitrogen dioxide, total suspended particles(TSP), and sulfur dioxide. RESULTS: Daily death counts were associated with ozone(1 day before), nitrogen dioxide(1 day before), TSP(2 days before), sulfur dioxide(2 days before). The association with ozone was most statistically significant and independent of other air pollutants. Increase of 100 ppb in ozone was associated with 6%(95% CI= 2%-10%) increase in the daily number of death. This effect was greater in persons aged 65 and older. The relative risks of death from respiratory disease and cardiovascular disease were greater than for all-cause mortality in each pollutant. After ozone level exceeds 25 ppb, the dose-response relationship between mortality and ozone was almost linear. However, the effect of TSP, sulfur dioxide, and nitrogen dioxide on mortality might be confounded with each other. CONCLUSION: Daily variations in air pollution within the range currently occurring in Seoul might have an adverse effect on daily mortality.