To evaluate the relative importance of various measures of particulate and gaseous air pollution as predictors of daily mortality in Inchon, South Korea, the association between total daily mortality and air pollution was investigated for a 20-month period (January 1995 through August 1996). Poisson regression was used to regress daily death counts on each air pollutant, controlling for time trends, season, and meteorologic influences such as temperature and relative humidity. Regression coefficients of a 5-day moving average of particulate matter less than or = to 10 microm in aerodynamic diameter (PM(10)) on total mortality were positively significant when considered separately and simultaneously with other pollutants in the model. PM(10) remained significant when the models were confined to cardiovascular or respiratory mortality. Sulfur dioxide (SO(2)) and carbon monoxide (CO) were significantly related to respiratory mortality in the single-pollutant model. Ozone exposure was not statistically significant with regard to mortality in the above models, and graphic analysis showed that the relationship was nonlinear. A combined index of PM(10), nitrogen dioxide, SO(2), and CO seemed to better explain the exposure-response relationship with total mortality than an individual air pollutant. Pollutants should be considered together in the risk assessment of air pollution, as opposed to measuring the risk of individual pollutants.