The effectiveness of a 20 session cognitive-behavioral approach to substance abuse prevention was tested on seventh grade students (n = 1,311) from 10 suburban New York junior high schools. The prevention strategy attempted to reduce intrapersonal pressure to smoke, drink excessively, or use marijuana by fostering the development of general life skills as well as teaching students tactics for resisting direct interpersonal pressure to use these substances. Additionally, this study was designed to compare the relative effectiveness of this type of prevention program when implemented by either older peer leaders or regular classroom teachers. Results indicated that the prevention program had a significant impact on cigarette smoking, excessive drinking, and marijuana use when implemented by peer leaders. Furthermore, significant changes were also evident with respect to selected cognitive, attitudinal, and personality predisposing variables in a direction consistent with non-substance use. These results provide further support for the efficacy of a broad-spectrum smoking prevention strategy and tentative support for its applicability to the prevention of other forms of substance abuse.