Air pollution has been associated with daily mortality in numerous studies over the past decade. However, most of these studies were conducted in the United States and Europe, with relatively few done in Asia. In this study, the association between ambient air pollution and daily mortality in Kaohsiung, Taiwan, a large industrial city with a tropical climate, was investigated for the period 1994-2000 using a case-crossover analysis. This design is an alternative to Poisson time-series regression for studying the short-term adverse health effects of air pollution. The air pollutants examined included particulate matter (PM10), sulfur dioxide (SO2), ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). No significant effects were found between PM10 and SO2 exposure levels and respiratory-related mortality. The well-established link between air pollution levels and daily mortality may not be as strong in cities in tropical areas, although other factors such as differences in pollutant mixtures or underlying health of the population may explain the lack of a strong association in this study. Further studies of this type in cities with varying climates and cultures are needed.