Tobacco and alcohol use among adolescents continue at historically high rates, and school-based interventions designed to deter students from smoking and drinking are increasingly being implemented. This study reports a meta-analysis of 47 smoking and 29 alcohol school-based intervention programs published after 1970. Results indicate that, in general, smoking and alcohol interventions have equally modest effects on immediate behavioral outcomes. Smoking interventions, however, have been more successful than alcohol interventions at altering students' long term behavior. All of the alcohol programs and all but one of the smoking programs reviewed successfully increased knowledge regarding the risks of these behaviors. Attitude change appears to be more difficult to achieve. Twenty-nine of 33 smoking studies and only 19 of 31 alcohol studies successfully changed students' attitudes. Finally, the data indicate that for immediate smoking outcomes and long-term alcohol outcomes innovative interventions relying upon social reinforcement, social norms, and developmental behavioral models are more effective than traditional "awareness" programs designed to inform adolescents about the health risks associated with tobacco and alcohol use. The implications of these findings for future of school-based health promotion programs are discussed.