School-based mentoring programs which utilize peer mentors have become a popular and cost-effective way of providing support services to students. While several studies examining mentee outcomes appeared in the past decade, less research has examined characteristics of the high school mentors involved. This study examined social interest, social self-efficacy, and general self-efficacy levels of high school volunteer mentors and their nonmentor peers, along with the effects of gender, prior mentoring experience, and experience as a mentee. Findings suggest higher levels of social self-efficacy, higher numbers of female volunteers, and higher rates of former mentees among mentor populations. (Contains 2 tables.)