ABSTRACT Although the fractions of station-days that the Pollutant Standard Index (PSI) exceed 100 (also referring to the episodes) in Kaohsiung City showed a decline trend from about 10.3% in 1995 to about 5.5% in 2002, the percentage of particulate PM10 events showed a increase trend: from 1.0 % in 2002 to 2.9 % in 2004. This study first statistically summarized the trends of PM10 concentrations using box plots for four air-quality monitoring stations in Kaohsiung during the period of 1997 to 2004, together with the t-test and F-test. The Comprehensive Air Quality Model with extensions (CAMx model) was then applied to analyze the source and the cause of the PM10 events. The monthly averages of PM10 concentrations at four air-quality monitoring stations were 72.9 ¡V 81.7 £gg/m3 during the period of 1997 to 2004, highest at Hsiung-Kong and lowest at Nan-Chie. The long-term trend analyses show slightly decline results for yearly-averaged PM10 concentrations (1.05% at Nan-Chie, 1.38% at Tzuo-Yin, 1.51% at Chien-Chin, and 1.91% at Hsiung-Kong). During 1997 to 2004, the PM10 episodes occurred most frequently, while the numbers of PM10 episodes decreased from south to north (i.e., Hsiung-Kong > Chien-Chin > Tzuo-Yin > Nan-Chie). The statistical tests using t-test for the mean and F-test for the variance with 95% confidence level show that the probability that the hourly PM10 concentrations differ insignificantly among the four stations is only about 42%. That is, the spatial difference of pollutant concentrations among four air-quality monitoring stations is rather significant in Kaohsiung. The CAMx simulations show that contributions to ambient PM10 from stationary source is about 38.9% (NOx: 24.7%; SO2: 14.2%), 8.8% from mobile source (NOx: 7.4%; SO2: 1.4%), and 0.9% from fugitive emissions (SO2: 0.9%) in Kaohsiung. The contributions to ambient PM10 from the emissions in Kaohsiung Harbor are about 3.5%. Keywords: Particulate matter, Trend analysis, Statistical test, CAMx model.