"Peer-to-peer" (P2P) programs involve people who might share the same age, sex, sexuality, social class, and/or subculture or other similarities in interactions and communication designed to guide behaviors and attitudes. P2P activities might include peer mentoring, peer assistance in meeting another peer's needs, and peer counseling. For the purposes of this guide, P2P involves youth bringing about positive change in other youth for the purpose of preventing drug abuse. The theoretical basis for emphasizing P2P drug prevention programs is that youth are more likely to listen to other youth than to adults. Further, youth are more knowledgeable about the circumstances and influences under which youth live; therefore, they are better able to tailor messages and actions to their peers. One of the most important factors in behavioral and attitudinal change is bonding with a person or group that provides role modeling and support for positive lifestyles. Such bonding is not as likely to happen in adult-dominated programs as in peer-dominated programs. In outlining the characteristics of a good P2P program, the guide indicates it must be culturally appropriate, developmentally appropriate, accurate in the information provided, based on experiential learning, and led by competent staff. The most important characteristic of such a program is that youth be involved in the program in more than just token ways. They should be involved in program design, leadership, monitoring, evaluation, and redesign. In addition to discussing the characteristics of an effective P2P program, this guide also addresses the following topics: how to design and plan an effective P2P program, how to select peer educators, how to match peers to the right P2P program, important skills for developing an effective program, developing the capacity to deliver the program, funding, evaluation, and how to be part of the Youthnet network. Resources and case studies and 19 references