Cross-age peer mentoring is a somewhat unique and different approach to mentoring than the better-known adult-with-youth mentoring model. In cross-age mentoring programs (CAMPs) the mentor is an older youth, typically high school-aged, who is paired or matched with an elementary or middle school-aged child. Meetings almost always take place in the school context, although there probably are countless camps, youth centers, and other youth organizations which informally, or for a short duration, pair younger youth with older youth for the purpose of providing the younger youth guidance, social support, or instruction. This article focuses primarily on one-to-one relationships between teenage mentors and younger mentees. Because descriptions and evaluation data on these programs in other contexts are infrequently reported in the research literature, it is unknown what the impact of such programs are or how their practice may vary from setting to setting. Additionally, no reports of cross-age peer mentors working with multiple youth in a group mentoring format were found in the literature search conducted to inform this article, making it difficult, at this time, to know how group peer mentoring programs operate and what potential benefits might be. Cross-age peer mentoring programs discusses were found to utilize structure, meet for more than ten meetings, do not focus primarily on deficit or problem reduction, and require an age span of at least two years. Cross-age peer mentoring, defined this way, has yielded positive effects for both mentors and mentees. The article is followed by suggestions on how practitioners can incorporate the research findings into mentoring programs and a list of additional resources. (Contains 2 figures and 1 table.) [The 10-issue "Research in Action" series, edited by Jean E. Rhodes, is the initial project of the MENTOR Research and Policy Council, charged with taking current mentoring research and translating it into useful, user-friendly materials for mentoring practitioners. For full series, see ED502220 through ED502229, inclusive.]