Several studies have reported the associations between airborne particles and/or ozoneand respiratory diseases. This study examined whether such an association could be seenin Seoul, one of the greatest city in Korea. We compiled daily records of hospital visits inSeoul from November 1, 1995 to October 31, 1996. The daily averages of ozone and parti-cle matter whose diameter is 10um or less(PM10) from all monitoring stations were com-puted. Daily respiratory hospital visits were regressed on temperature, humidity, day ofweak indicators, seasonal variation indicators, and air pollution. Each pollutant was firstexamined individually and then two pollutant models were fitted.Results : Both PM10 and Ozone were associated with increased risk of respiratory hospi-tal visits. The relative risk of respiratory hospital visits for 50 ug/m^3 increase inPM10(lagged 2 days) was 1.11(95% confidence interval: 1.05-1.18). The PM10 associationswas insensitive to alternative methods of control for weather, including exclusion ofextreme temperature days and control for temperature on another day. The ozone resultswere more sensitive to the approach for weather control. The relative risk of respiratoryhospital visits for 0.01 ppm increase in O3 was 1.08(95 % confidence interval 1.00-1.17).The magnitude of the PM10 effect in Seoul, where SO2 was essential present, was similarto that reported in the Europe and United states.In conclusion. The consistency of investigations of the health effects of air pollutionsuggest that attention should be paid to the control of air pollution.