The HBSC research network is an international alliance of researchers that collaborate on the cross-national survey of school students: Health Behaviour in School-aged Children (HBSC). The HBSC collects data every four years on 11-, 13-, 15 year-old boys' and girls' health and well-being, social environments and health behaviours. It is carried out in close cooperation with WHO-Europe. HBSC now includes 51 countries and regions across Europe (including Latvia) and North America. HBSC focuses on understanding young people's health in their social context – where they live, at school, with family and friends. Researchers in the HBSC network are interested in understanding how these factors, individually and together, influence young people's health as they move from childhood into young adulthood. The international standard questionnaire produced for every survey cycle enables the collection of common data across all participating countries and thus enables the quantification of patterns of key health behaviours, health indicators and contextual variables. These data allow cross-national comparisons to be made and, with successive surveys, trend data is gathered and may be examined at both the national and cross-national level.