Through this international report on the results of its most recent survey, the Health Behaviour in School-aged Children (HBSC) study aims to supply the up-to-date information needed by policy-makers at various levels of government, nongovernmental organizations, and professionals in sectors such as health, education, social services, justice and recreation.The report presents findings from the 2009/2010 survey on the demographic and social influences on the health of young people (aged 11, 13 and 15 years) in 43 countries and regions in the WHO European Region and North America. Statistical analyses were carried out to identify meaningful differences in the prevalence of health and social indicators by gender, age group and levels of family affluence. The aim was to provide a rigorous, systematic statistical base for describing cross-national patterns in terms of the magnitude and direction of differences between subgroups.