This volume is a guide to providing effective Human Immunodeficiency Virus (HIV) and substance abuse prevention services to runaway and homeless youth. The guide is based on current research and the best programs in this field. Chapters 1 and 2 summarize what is known about runaway and homeless youth, the services these youth require if they are to reduce their risk behaviors, and the challenges of integrating HIV prevention activities into existing programs. Chapter 3 on program planning covers: developing goals and policies for programs, assessing needs, designing prevention activities, distributing condoms, educating staff and volunteers, evaluating prevention activities, and implementing HIV antibody testing. Chapters 4 through 6 use a case study approach to describe three types of programs: (1) those that serve the "street youth" of larger cities (Los Angeles Youth Network, Urban Peak in Denver, Colorado, and Streetwork Project in New York, New York); (2) short-term crisis intervention services (The Bridge for Runaway Youth in Minneapolis, Minnesota, and Huckleberry House in Columbus, Ohio); and (3) a system of comprehensive care for runaway and homeless youth coordinated by the Division of Adolescent Medicine of the Childrens Hospital of Los Angeles. The guide includes a bibliography and list of resources. (Contains 214 references.) (JB)