This study reports on CHAMPS, a youth tobacco and prevention program intervention that focused on peer-led educational activities. Nineteen schools implemented a CHAMPS tobacco prevention program in grades 5, 6, and 7. Six schools served as nonintervention comparison sites. Baseline and follow-up questionnaires were completed by 1,412 students. The proportion of students reporting current cigarette use decreased significantly in the CHAMPS group but not in the comparison group. Intervention group students' knowledge about the harmful consequences of tobacco use increased significantly, whereas knowledge essentially stayed the same among comparison group students. Finally, the number of nonsmoking students who reported they would smoke a cigarette if one of their best friends offered it increased significantly in the comparison group but not in the intervention group. These results suggest that a well-planned and implemented peer-helping program represents an important potential resource that should be considered as a welcome adjunct to existing school-based tobacco education and prevention efforts. (Contains 1 table.)