UNSPECIFIEDThe Centers for Disease Control and Prevention (CDC) developed this Compendium of HIV Prevention Interventions with Evidence of Effectiveness to respond to prevention service providers, planners, and others who request science-based interventions that work to prevent HIV transmission. All interventions selected for this Compendium came from behavioral or social studies that had both intervention and control/comparison groups and positive results for behavioral or health outcomes. We required designs with control/comparison groups so that successful results could be attributed to the interventions. Appendix A describes in detail the criteria used to select the interventions. This document provides Summaries of each intervention that met all criteria. These are referred to as effective interventions. To meet the ongoing need for current information about what works in HIV prevention, this Compendium will be updated periodically. The Compendium provides state-of-the-science information about interventions with evidence of reducing sex- and/or drug-related risks, and the rate of HIV/STD infections. These interventions have been effective with a variety of populations, e.g., clinic patients, heterosexual men and women, high-risk youth, incarcerated populations, injection drug users, and men who have sex with men. They have been delivered to individuals, groups, and communities in settings such as storefronts, gay bars, health centers, housing communities, and schools. A reader may want to consider an entire group of studies, for instance, all studies that used small group interventions. Table 1 highlights population and intervention characteristics for each of the interventions. Accessing additional materials may assist in implementing a selected intervention. Table 2 indicates the interventions that are part of CDC's Replicating Effective Programs (REP), Prevention Counseling Course Series, and Research to Classroom: Programs That Work (PTW) projects. These ongoing projects support development of intervention materials, training, and technical assistance. Once an intervention is adopted, its actual impact will depend on how it is implemented. The important thing is to achieve a balance between adapting the intervention to suit local needs and maintaining the core elements and key characteristics that made the original intervention successful. Also, the agency that implements the intervention will require organizational support, adequate staffing, and sufficient resources for implementation. Finally, some readers may prefer an alternative or additional approach. They may want to assess and strengthen their existing program activities rather than select a new intervention, or to do both. We offer an Intervention Checklist to guide this process. The items on the Checklist are derived from many successful prevention interventions.HIV/AidsHealth Risk FactorsSexual HabitsinterventionsResearchstudiesCenters for Disease ControlHIV transmissionHIV preventionreducing sex- and/or drug-related risksOther