What is sex education? Who should teach it? What are the most effective strategies? When and where should it be taught? These are just some of the questions to be examined in this lecture. After three decades research and international experience, much has been learned about how to best to teach about sex, sexuality and relationships. Despite this, there remains controversy and few countries have implemented the kinds of programs that are known to be effective. The conflict between science and strongly held beliefs makes reasoned and rational discussion difficult. So, what should we do next?