This review article questions the assumptions at the core of peer education interventions adopted in young people's sexual and reproductive health programmes in developing countries. Peer education is a more complex and problematic approach than its popularity with development agencies and practitioners implies. Its rise to prominence is more indicative of the desire to find effective tools to address the HIV/AIDS pandemic, than of peer education's proven effectiveness. The often simplistic model of social relations that underlies peer education interventions leads to the reinforcement of gendered power relations, and a failure to take account of the social dynamics of poverty. The dominant rationales for peer education are examined and contested. In spite of the mismatch between rhetoric and experience, the appeal of the approach remains powerful, stemming largely from the objective of engaging young people in health interventions in a way that increases their autonomy and capacity.