Objective: To describe the development of the National Institute for Health and Clinical Excellence (NICE) evidence-based guidance on one-to-one interventions for prevention of STIs and under 18 conceptions, as a focus for an integrated approach to sexual health services. Method: Documentation of the process for developing NICE guidance that is "evidence based" and "independent". Stages were: scoping the focus of the guidance; critical appraisal and synthesis of different types of evidence; economic modelling; preparation of draft recommendations; field testing their relevance and feasibility for implementation in the English context. Results: The best available evidence demonstrates that one-to-one structured discussions with practitioners offer an effective means to support vulnerable young people and those at risk of STI infection to change their sexual behaviour and reduce their level of risk. Economic modelling demonstrated that many forms of one-to-one interventions can be cost-effective, including those involving sessions of structures discussion or counselling. Recommendations integrate the identification of high-risk groups and the need to offer information and advice on prevention of STIs including HIV and under 18 conceptions into the mainstream of heath and other services. Conclusion: Although one-to-one interventions are a comparatively narrow component of a strategic programme for the prevention of STIs and under 18 conceptions, this focus is central to addressing these challenges. This supports a much more integrated approach to service provision, within the context of modernization of sexual health services. (Contains 1 table and 3 figures.)