What contextual factors affect the success of HIV-prevention in schools? What are the most appropriate strategies for creating contexts that support the success of schools-based efforts to reduce HIV-transmission? This paper examines current research, policy and practice in youth HIV-prevention, pointing to gaps in understanding that hamper the design, implementation and evaluation of interventions. Firstly we outline the goals of peer education, the most popular youth HIV-prevention approach, pointing to contextual factors that impact on programme success. Secondly, we review research into contextual influences on programme outcomes, highlighting its fragmented and descriptive nature, and the need for comprehensive frameworks to pull together findings in ways that could better guide research and practice. Thirdly we examine the policy context within which youth HIV education is currently delivered, and some concrete examples of youth-oriented initiatives. Running throughout the discourses of researchers, policy-makers and programme designers is a shared belief in the value of community mobilisation (including the strategies of 'participation' and 'partnerships') for promoting contexts most likely to support health-enhancing behaviour change. Yet references to these strategies remain vague and unsystematic, with little formal attention to the types of social relationships that they should seek to build, and little acknowledgement of the complexities of implementing them. In conclusion, we point to the concepts of bonding, bridging and linking social capital as useful starting points for conceptualising the types of types of social relationships that effective 'participation' and 'partnership' strategies should aim to promote.2