This study was designed to assess the level of nitrogen dioxide from several microenvironments including inside the home, outdoors near the home, inside the school, outdoors near the school, and on the road for 42 primary schoolchildren during the month of December 2002 in Seoul, Korea. The average personal, indoor, outdoor $NO_2$ levels, and indoor/outdoor ratio were 45.08 ppb, 27.89 ppb, 30.96 ppb, and 0.89, respectively. The indoor $NO_2$ concentrations were significantly associated with the presence of a smoker with a gas stove. The estimated personal $NO_2$ exposure using time-weighted average equation of $34.64{pm}5.29$ ppb was significantly lower than the measured personal exposure of $45.08{pm}5.50$ ppb. Our results indicate that indoor $NO_2$ levels were associated with the presence of a smoker and a gas stove. Moreover, personal $NO_2$ exposure with a gas stove in the house was significantly higher than those without a gas stove.