Increasing demands for sex education have been associated with a plethora of recommendations, regulations and resources with resulting variability of content, strategy, quality and outcome. While numerous studies confirm that the health behaviour of teenagers is not altered by the teaching of facts alone, other data suggest that appreciation of personal risk and learned assertiveness skills are associated with changes in population behaviours. Peer led teaching is a powerful and probably essential component of school health and sex education. Evaluated interventions with agreed purpose and acceptable methodologies are essential if there is to be any real expectation of health benefit from sex education.