Characteristics of PM1/PM2.5/PM10 were evaluated in the ambient general (Chung-Shan) and traffic (Da-Tung) monitoring stations in the Taipei area. It was observed that average concentrations of PM1, PM2.5, and PM10 were 14.0, 24.4, and 48.1 g/m3 in the Chung-Shan station, respectively. In the Da-Tung station, the mean levels of PM1, PM2.5, and PM10 were 37.6, 42.8, and 61.5 g/m3, respectively. In addition, it was found that PM1/PM2.5 mass ratios could be as high as 0.90 in the traffic station. Regarding carbon profiles, it was observed that mass fractions of total carbon in PM1, PM2.5, and PM10 were 0.58, 0.49, and 0.35 in the Chung-Shan station and 0.74, 0.66, and 0.53 in the Da-Tung station, respectively. It was clearly indicated that fine particles related to combustion sources play an important role in urban atmosphere. Further investigation is needed to evaluate chemical compositions and health effects of PM1.