Studies have begun to document the academic and psychosocial benefits of Big Brothers/ Big Sisters programs for at-risk youth (Rhodes, Grossman, & Resch, 2000). However, investigators have noted a problem with mentor attrition (Meissen & Lounsbury, 1981). The purpose of the current study was twofold. First, we explored the relative importance of specific dimensions of perceived similarity (including similarity in attitudes, interests, race, and personality) as well as mentors' expectation-reality discrepancies in predicting mentors' expressed intention to remain in Big Brothers/Big Sisters programs. Second, we examined a model whereby interpersonal attraction and relationship quality served as mediators of these associations. Our results suggest that perceived similarity in extraver-sion as well as the discrepancy between mentors' ideal versus actual roles were significant predictors of mentors' expressed intention to remain in the relationship. Relationship quality and interpersonal attraction appeared to mediate these findings.