This volume brings together the findings from separate studies of community-based and school-based mentoring to unpack the common response to the question of what makes youth mentoring work. A debate that was alive in 2002, when the first New Directions for Youth Development volume on mentoring, edited by Jean Rhodes, was published, centers on whether goal-oriented or relationship- focused interactions (conversations and activities) prove to be more essential for effective youth mentoring. The consensus appeared then to be that the mentoring context defined the answer: in workplace mentoring with teens, an instrumental relationship was deemed essential and resulted in larger impacts, while in the community setting, the developmental relationship was the key ingredient of change. Recent large-scale studies of school-based mentoring have raised this question once again and suggest that understanding how developmental and instrumental relationship styles manifest through goal-directed and relational interactions is essential to effective practice. Because the contexts in which youth mentoring occurs (in the community, in school during the day, or in a structured program after school) affect what happens in the mentor-mentee pair, our goal was to bring together a diverse group of researchers to describe the focus, purpose, and authorship of the mentoring interactions that happen in these contexts in order to help mentors and program staff better understand how youth mentoring relationships can be effective. This is the 126th issue of New Directions for Youth Development the Jossey-Bass quarterly report series dedicated to bringing together everyone concerned with helping young people, including scholars, practitioners, and people from different disciplines and professions. The result is a unique resource presenting thoughtful, multi-faceted approaches to helping our youth develop into responsible, stable, well-rounded citizens.