Commentary. The Health Behaviour in School-aged Children (HBSC) study has informed the development and implementation of policy for children and adolescents for over three decades. The growing recognition that adolescence is a critical period for later health and well-being has highlighted the need for, and importance of timely and accurate data. Every 4 years, the HBSC study provides evidence on health behaviors, health outcomes, and social environments of boys and girls across Europe and North America. To maximize the impact of evidence, the HBSC study has a working Policy Development Group that cultivates relationships with key stakeholders, disseminates widely HBSC research, and facilitates discussion and cross-fertilization of ideas and priorities. To date, HBSC data have been central to health promotion efforts and developments in practice, policy, and legislation at both national and international levels.