Over the past 25 years, the WHO collaborative cross-national Health Behaviour in School-aged Children (HBSC) study has been accumulating evidence that provides insights into how to promote the health and well-being of young people. HBSC has increased understanding of the determinants of young people's health, particularly in relation to the social contexts in which they live, learn and play. The study now spans 43 countries and regions in Europe and North America. HBSC provides intelligence for the development and evaluation of public health policy and practice at national, sub-national and international levels. However, the mere existence of evidence does not automatically change policy nor necessarily improve the lives of young people. Effective mechanisms to ensure use of evidence in policy-making and practice are needed. The WHO/HBSC Forum series is a platform designed to facilitate the translation of evidence into action. Forum processes convene researchers, policy-makers and practitioners from across Europe to analyse data, review policies and interventions, and identify lessons learned to improve the health of adolescents through actions that address the social contexts that influence their health. Each Forum process consists of case studies produced by interdisciplinary teams in countries and regions, cross-country evidence reviews, a European consultation, an outcomes statement within a final publication, and a Web-based knowledge platform. In addition to emphasizing the translation of research into action, the Forum series focuses on increasing know-how to scale up intersectoral policies and interventions; reduce health inequities; and involve young people in the design, implementation and evaluation of policies and interventions. Interviews with selected participants in the 2007 Forum process revealed that national-level impacts of involvement were: brokering new or strengthening existing working relationships among members of case study drafting teams and national delegations to events; feeding into the formulation of national policy or practice design; and enabling the comparison of information systems, policies, interventions, and working methods with other countries and against the evidence base, thus providing encouragement for new and/or validation of existing activities. The WHO/HBSC Forum series is an evolving platform. The methodology for each Forum process incorporates lessons learnt through past Fora - within resource constraints - and is based on the principles of efficiency and effectiveness. Areas requiring further development, identified through the aforementioned interviews and based on the reflections of co-organizers, include identification of means to ensure systematic, appropriate and meaningful youth involvement; maximization of the usefulness of the European consultation; and definition of a budget line and framework for evaluation of the process' impact at country level.