This study presents one-year follow-up data from an evaluation study testing the effectiveness of a cognitive-behavioral substance abuse prevention approach which emphasizes the teaching of social resistance skills within the larger context of an intervention designed to enhance general social and personal competence. The follow-up study involved 998 eighth graders from 10 suburban New York junior high schools. Two schools were assigned to each of the following conditions (a) peer-led intervention, (b) peer-led intervention with booster sessions, (c) teacher-led intervention, (d) teacher-led intervention with booster sessions, and (e) control. The original intervention was implemented in the seventh grade; the booster intervention was implemented during the eighth grade. Results indicate that this type of prevention strategy, when implemented by peer leaders in the seventh grade and when additional booster sessions are provided during the eighth grade, can reduce tobacco, alcohol, and marijuana use. Similar effects are evident for females when the prevention program is implemented with fidelity by classroom teachers. Moreover, the prevention program is also capable of producing a significant impact on several hypothesized mediating variables.