Differences between community-based and school-based mentoring programs were investigated, as well as whether enough mentors in both types of programs were developing close and supportive relationships with young people and specific benchmarks mentoring programs used to ensure the optimum development of supportive relationships. It was found that mentors in community-based and school-based programs received the same amount of training, but school-based programs implemented many programmatic changes to the traditional model that reduced costs and involved adults who would not typically mentor. Mentors in school-based programs spent more time doing homework with young people, had more contact with teachers, and felt more effective in influencing educational achievement. In community-based programs, mentors spent more time engaging in social activities, had more contact with parents, and felt more effective in influencing social behavior. Mentors in community-based programs were overwhelmingly between 22 and 49 years of age, while those in school-based programs spanned the age spectrum. School-based programs delivered less contact hours than community-based programs and they were significantly less expensive per youth, $567 compared to $1,369 annually. Over 90 percent of mentors in both community-based and school-based programs said they felt close to their mentees. The authors suggest that a school-based approach to mentoring provides a promising complement to the traditional community-based model, and they discuss benchmarks of effective mentoring programs. Appendixes include a list of members in the Public Policy Council of the National Mentoring Partnership and a description of methods used to evaluate mentoring programs. 20 references, 6 endnotes, and 12 tables