The purpose of this paper is to conduct a review of reviews to identify characteristics of effective sex and relationship education (SRE) interventions and/or programmes in young people to improve sexual health and identify barriers and facilitators for implementation. Six bibliographic databases were searched from 1986 to 2006 for systematic reviews that assessed SRE interventions or programmes in participants between 10 and 18 years old and their partners. All outcomes of improvement in sexual health were assessed and 30 systematic reviews were included. Effective interventions and/or programmes tended to be those targeting younger age groups before they become sexually active, focused interventions tailored to the physical and biological development stages, theory based, and abstinence education programmes that incorporate values of relationships and provide skills training and links to contraceptive services. Adequate training of personnel delivering the interventions and culturally sensitive programmes were identified as important facilitators of effectiveness. Future research should explore the appropriate age for initiating sex education and investigate targeting specific behaviour compared with multiple-outcome targeting. Research exploring the reasons for interventions focusing on specific populations (i.e. African and Hispanic origins), even if they were conducted in countries dominated by Caucasians, is warranted. (Contains 4 tables.)