Youth mentoring refers to a relationship between youth -- particularly those most at risk of experiencing negative outcomes in adolescence and adulthood -- and the adults who support and guide them. The origin of the modern youth mentoring concept is credited to the efforts of charity groups that formed during the Progressive era of the early 1900s to provide practical assistance to poor and juvenile justice-involved youth, including help with finding employment. Approximately 2.5 million youth today are involved in formal mentoring relationships through Big Brothers Big Sisters (BBBS) of America and similar organisations. Contemporary mentoring programs seek to improve outcomes and reduce risks among vulnerable youth by providing positive role models who regularly meet with the youth in community or school settings. Some programs have broad youth development goals while others focus more narrowly on a particular outcome. Evaluations of the BBBS program and studies of other mentoring programs demonstrate an association between mentoring and some positive outcomes, but the effects of mentoring on particular outcomes and the ability for mentored youth to sustain gains over time are less certain. This book begins with an overview of the purpose of mentoring, including a brief discussion on research of structured mentoring programs. The book then describes the evolution of federal policies on mentoring since the early 1990s and provides an overview of the components and funding for each of two recent (discontinued) federal mentoring programs, as well as a discussion of other federal mentoring initiatives that are currently funded.