A guide to indicators for monitoring and evaluating national HIV/AIDS prevention programmes for young people has been developed in collaboration with UNAIDS cosponsors and a wide range of other partners to provide an overview of core indicators that should be used at national level to monitor and evaluate programmes directed to HIV prevention among young people. The indicators have been classified in line with the CAH Mapping Adolescent Programme and Measurement (MAPM) framework, and the Guide includes indicators focusing on health outcomes, underlying behaviours, determinants that give rise to these behaviours, and interventions directed to changing these determinants. Although some of the indicators included in the Guide are still being refined and field tested, for each of the indicators included in the Guide there are details of what they are, why they should be used, how they can be measured, and their strengths and limitations.