This study aimed at examining the risk factors of smoking behavior among middle school students and preparing school-based smoking prevention program. This study surveyed at February 1995 from 892 students at 3 middle schools in Seoul. The major findings of this study are follows; The proportion of current smoker among students in this study was 3.8%, and the proportion of intentions to smoking was 8.4%. At demographic variables male, pocket money of month was significantly positive association with smoking behavior, but economic status and education status of father were significantly negative association with smoking behavior. Results indicated that social influence variables(peer influence), alcohol, and positive attitudes of smoking were significantly positive association with smoking behavior. So implications for smoking prevention programs may be more effective at risk populations than using general adolescent population. Also ‘School-based smoking prevention programs’ may be learning social pressure resistance skills and giving knowledge and information about negative attitudes about smoking.