Psychosocial smoking prevention studies have shown inconsistent results and theory-driven programs have been related to program success. This meta-analysis was used as a judgment tool for resolving these issues by estimating average program effects and investigating the relative efficacy of program types. The present study examined 65 adolescent psychosocial smoking prevention programs (1978 to 1997) among students in Grades 6 to 12 in the United States. Three program modalities (social influence, cognitive behavior, life skill) and two program settings (exclusively school based, school-community-incorporated)were identified as major a priori classifications. Knowledge had the highest effect sizes (.53) at short-term (up to 1 year) but rapidly decreased (.19) at long-term (over 1 year). Behavioral effect was the most meaningful, being persistent over a 3-year period (.19 at up to 1 year; .18 at 1 to 3 years). Adolescent smoking reduction rates were increased by using either cognitive behavior or life skills program modalities, and/or a school-community-incorporated program setting. (Contains 4 tables.)