The case-control study followed the entire seventh grade cohort of 30 junior high schools in 8 urban, suburban, and rural communities in California and Oregon between 1984 and 1986. Among subjects who had not tried cigarettes or marijuana before baseline, the group which had received the educational program showed a significantly lower rate of initiation into or regular use of cigarettes and marijuana than the control group at 3-, 12-, and 15-month follow-ups. The program was successful for both low- and high-risk students and equally for schools with high and low minority enrollment, but did not curb previously confirmed cigarette smokers and had only short-lived effect on drinkers. 5 tables, 32 references.