This research brief highlights studies of nationally- and locally-based youth mentoring programs. The programs were evaluated on an experimentally based design which compared a group of youth randomly assigned to a mentoring program with a group of youth who were not so assigned. The study found overall that mentoring programs can be effective tools for enhancing the positive development of youth. Mentored youth are likely to have fewer absences from school; better attitudes towards school; fewer incidents of hitting others; less alcohol and drug use; and improved relationships with their parents or caregivers. One cautionary note was that mentoring of short duration might do more harm than good. Considerations that policymakers and practitioners may want to keep in mind are addressed. The most important policy consideration suggested is that, in general, mentoring programs are worth the investment. (Contains 19 references.) (JDM)