In 1995, WHO in collaboration with UNFPA and UNICEF convened a study group on programming for adolescent health and development. One of the products of this group was a joint technical report publication on Programming for adolescent health and development. The report synthesized the evidence for the effectiveness of interventions for adolescent health and development, and it set the direction and provided the conceptual framework for much of the programming for young people's health and development that has taken place since its publication.The challenges posed by HIV have progressed inexorably during the past decade, especially for young people in developing countries. (Young people are defined in this report as those aged 10-24 years; this group combines adolescents - aged 10-19 years - and youth - aged 15-24 years). At the same time, many lessons have been learnt about developing and implementing programmes for young people's health and development, including programmes to prevent the spread of HIV. In 2004, the UNAIDS Inter-Agency Task Team on Young People decided that it was time to review the progress that had been made and to look again at the evidence for the effectiveness of interventions, focusing explicitly on interventions to prevent the spread of HIV among young people in developing countries.This report is an attempt to rise to the challenge by providing systematic reviews of the evidence for policies and programmes to decrease HIV prevalence among young people, as a contribution towards achieving universal access to prevention, treatment and care and attaining the Millennium Development Goal on AIDS.