A grade five through eight substance abuse prevention program, later incorporated into the Michigan Model for Comprehensive School Health Education, was developed, implemented, and evaluated. Results focus on students who received seven lessons on alcohol in grade six, and eight lessons on tobacco, alcohol, marijuana, and cocaine in grade seven taught by their regular classroom teachers (after a 6-hour training in the social pressures resistance skills curriculum). Students (N = 442) received either two years of the program or none, and completed individually-coded questionnaires. Repeated measures analysis of variance resulted in significant treatment by occasion interactions on the use of alcohol, cigarettes, marijuana, cocaine, and other drugs, as well as on knowledge. At the end of grade seven, program students' rates of substance use had increased significantly less and knowledge of alcohol pressures, effects, and skills to resist had increased significantly more than those of comparison students.