Parents are the central source of emotional, financial and social support for their children. Many young people also have the benefit of relationships with adults other than parents--including teachers, coaches, grandparents, older siblings, neighbors and employers--who serve as informal mentors. These relationships provide youth with extra attention, affection, guidance and a sense of direction and self-worth--all of which are increasingly important given the wide array of outside influences, not all of them positive, that face young people today. Once viewed as a natural process that took place in the immediate or extended family, mentoring has become an increasingly popular strategy for enhancing the academic, social and emotional development of middle and high school students, particularly those at risk of underachievement. Today, there are nearly 5,000 volunteer-based youth mentoring programs operating nationwide, sponsored by government agencies, school districts, businesses, universities, professional organizations and nonprofit groups. Such programs give students stronger incentives for staying in school, avenues for exploring education and career paths, exposure to positive social norms, and access to the guidance and support of a caring adult. But research also provides evidence of the potential adverse effects of programs targeting at-risk youth that are poorly designed and managed. Mentoring relationships cut short by unclear or conflicting expectations, lack of support and other problems "may do more harm than good." This issue of "The Progress of Education Reform" focuses on: (1) an overview of different types of mentoring programs; (2) benefits and potential adverse effects of mentoring programs; and (3) mentoring as part of schoolwide reform efforts. Summaries of four articles on mentoring and links to other Web sites are also included.