This study explores the applicability of different conceptual models to two different policy sectors in Scotland; education and health, with specific reference to SHARE a specially designed school sex education programme. The study also draws on the policy network literature to understand the way in which the interaction between organisations and actors affects the value attached to research evidence. This thesis addresses three main research questions: How has school sex education policy been developed? How is research evidence used in school sex education policy development since devolution? What factors facilitate or impede the use of research evidence? To explore these issues I carried out 21 in-depth semi-structured interviews with policy makers and researchers, all of whom had insight into various aspects of sex education policy development in health and education. Using semiotics, I also analysed four policy documents. Results The development of sex education policy in the health and education sectors appears to have different underlying objectives. In the health sector it is designed to achieve immediate action, which requires speedy decision-making, while in the education sector it is designed to build consensus, achieved through cautious and careful decision-making. In health leadership of policy development for sex education can be identified at the instigation of policies with a high turnover of actors in subsequent stages; leadership within education is controlled and maintained throughout all stages of sex education policy development. As a result, common epistemic perspectives are more easily identified amongst those developing sex education within education, than within health. These perspectives affect the way research evidence has been used in the development of sex education policy. Although research evidence has been used in different ways, the intention behind its use is nearly always political. Fast decision-making militates against the use of research evidence in the health sector, while prioritising consensus overshadows the need to be evidence-based in education. The use of research in sex education policy-making is inhibited or facilitated by external contextual factors (political and organisational priorities) and internal contextual factors (modes of decision-making, the beliefs and interests of individuals, and interaction between individuals). In addition, the dynamics of power between policy-makers and researchers need to be carefully negotiated and can also be influenced by contextual factors.