Across Ages is a school- and community-based substance abuse prevention program for youth ages 9 to 13. The unique feature of Across Ages is the pairing of older adult mentors (55 years and older) with young adolescents, specifically those making the transition to middle school. The overall goal of the program is to increase protective factors for high-risk students to prevent, reduce, or delay the use of alcohol, tobacco, and other drugs and the problems associated with substance use. The four intervention components are (1) a minimum of 2 hours per week of mentoring by older adults who are recruited from the community, matched with youth, and trained to serve as mentors; (2) 1-2 hours of weekly community service by youth, including regular visits to frail elders in nursing homes; (3) monthly weekend social and recreational activities for youth, their families, and mentors; and (4) 26 45-minute social competence training lessons taught weekly in the classroom using the Social Problem-Solving Module of the Social Competence Promotion Program for Young Adolescents developed by Roger Weissberg and colleagues. Implementing Across Ages requires a full-time project coordinator, a part-time outreach coordinator, and one mentor for every one or two students.