The effectiveness of a fifteen session psychosocial smoking prevention strategy was tested on 902 seventh graders from seven junior high schools in suburban New York over 2 years. The prevention program was implemented by regular classroom teachers and consisted of a cognitive component dealing with the immediate consequences of cigarette smoking, a decision-making component, a relaxation-training component, a social skills training component, and a self-improvement component. In addition to testing the overall effectiveness of this approach, the relative efficacy of two different scheduling formats was compared and the extent to which "booster" sessions conducted during the year after completion of the program helped to maintain reductions in new smoking was also examined. Results indicated that the prevention program was able to reduce new cigarette smoking by 50% at the end of the first year and by 55% at the end of the second year for the intensive format condition. New regular cigarette smoking was reduced by 87% in the second year for the students in the booster condition. Significant changes consistent with nonsmoking were also evident on several cognitive, attitudinal, and personality variables.