In this study, the authors compared group members' and group outsiders' susceptibility to the influence of their friends' smoking. Ss were nonsmokers in Grade 7 who were observed for 1 year. Consistent with their hypothesis, the authors found that group outsiders (Ss who did not have reciprocal friends) were affected more by the smoking of their best friend and by the overall level of smoking among their friends than group members were. Furthermore, this peer influence was strongest for teens who were very concerned about their friends' reactions to their substance use. In addition, consistency in smoking status was related to the formation, but not the breakdown, of reciprocal friendships. Results indicated that teenagers may view smoking as a vehicle for entering a desired friendship group. The authors suggest ways that prevention programs might address this mechanism for adolescent smoking initiation.