The findings show that both perceived peer and friend cigarette use predicted participants’ own cigarette use within and across the adolescent years. For an adolescent’s alcohol and marijuana use, perceptions of peer and friend use were limited in their influence primarily to middle school. These findings suggest that strategies for preventing peer and friend influences on substance use should receive strong emphasis in the middle-school years. The findings also suggest the possibility that cigarette use may be a behavioral impetus for peer group acceptance that is unlike other drug use. Once begun, this may have lasting adverse effects throughout adolescence. Study participants were sixth and seventh graders from eight schools in Kansas City, MO, who composed a panel for longitudinal followup. Outcome measures were the frequency of weekly use of cigarettes, alcohol, and marijuana. Friends’ use was measured by asking how many of the student’s close friends used cigarettes, alcohol, or marijuana. In measuring perceived peer use, students were asked, “Out of every 100 students your age, how many do you think smoke cigarettes/or drink alcohol/or use marijuana at least once a month?” 1 table, 6 figures, and 56 references