A smoking prevention program for adolescents conducted in two public middle schools focused on resisting peer pressure to smoke and understanding the intent of commercial cigarette advertising. One class in each school participated in the program group and one served as a control group. The program consisted of eight sessions and was conducted by first-year medical students. Data on smoking behavior and related information were obtained from self-administered questionnaires at baseline, at the conclusion of the program, and one year later. One year after the program was concluded, the proportion of non-smokers was higher among those who had participated in the program than among the controls. This suggests that routine implementation of smoking prevention programs in conventional school settings may be productive in reducing the prevalence of cigarette smoking.