The purpose of this study was to investigate the concentration and distribution characteristics of $PM_{10}$ at high schools classrooms in Ulsan and its surroundings. This study evaluated $PM_{10}$ levels in classrooms at 79 high schools in Ulsan from May 2008 to May 2009. The average $PM_{10}$ level was 63.8 ${mu}g/m^3$, and the rate of exceeding the statutory maintenance limit was 16.0%. The average $PM_{10}$ level was higher in general schools (64.9 ${mu}g/m^3$) compared to professional schools (59.2 ${mu}g/m^3$), and private schools (66.6 ${mu}g/m^3$) was higher than that of public schools (62.5 ${mu}g/m^3$). The average $PM_{10}$ level (68.4 ${mu}g/m^3$) in general classrooms was significantly (p < 0.01) higher than that in multi-purpose ones (54.6 ${mu}g/m^3$), and first-year student classrooms (73.3 ${mu}g/m^3$) was significantly (p < 0.05) higher than that in second or third grade ones (67.6 ${mu}g/m^3$, 51.5 ${mu}g/m^3$, respectively). The $PM_{10}$ level in schools in Dong-Gu in the vicinity of assorted industrial complexes was higher than that of schools located in other districts around the Ulsan Metropolitan Area. The regression model showed that $PM_{10}$ level was positively associated with number of students and relative humidity.