The Media Ready Program was designed as a middle school, media literacy education, preventive intervention program to improve adolescents' media literacy skills and reduce their intention to use alcohol or tobacco products. In a short-term efficacy trial, schools in North Carolina were randomly assigned to conditions (Media Ready: n = 214; control: n = 198). Boys in the Media Ready group reported significantly less intention to use alcohol in the future than did boys in the control group. Also, students in the Media Ready group who had used tobacco in the past reported significantly less intention to use tobacco in the future than did students in the control group who had previously used tobacco. Multilevel multiple mediation analyses suggest that the set of logical analysis Message Interpretation Processing variables mediated the program's effect on students' intentions to use alcohol or tobacco in the future.