This paper analyzes the literature on mentoring for adult and youth populations for the following purposes: (1) to apply issues and concerns found in the literature to mentoring programs for disadvantaged and tenacious youth; and (2) to establish assumptions and program principles beyond the considerations of the existing literature. Chapter I, "The Basis and Functions of Planned Mentoring," distinguishes between natural (non-parental, unstructured) and planned (formal, programmatic) mentoring and examines the psychological bases of the mentoring process as well as the social values inherent in mentoring programs. Chapter II, "Mentoring in Organizations," describes natural and planned mentoring in the forum where they first became popular, and explores the shortcomings and benefits of their application to youth mentoring. Chapter III, "Planned Mentoring for Tenacious and Other Youth," discusses formal mentoring programs for disadvantaged youth and explores such issues as program organization and mentor-mentee match. Chapter IV, "The Power of Mentoring," focuses on the salience of the mentoring relationship and examines its place within larger multi-intervention programs. Chapter V, "Summary and Conclusions," contains general observations on youth mentoring programs and policy recommendations for their conduct. A list of 81 references, and the names of 64 organizations and programs consulted, are appended. (AF)