UNLABELLED: What is already known about this subject Overweight and obesity prevalence estimates among children based on International Obesity Task Force definitions are substantially lower than estimates based on World Health Organization definitions. Presence of a north-south gradient with the highest level of overweight found in southern European countries. Intercountry comparisons of overweight and obesity in primary-school children in Europe based on measured data lack a similar data collection protocol. What this study adds Unique dataset on overweight and obesity based on measured weights and heights in 6-9-year-old children from 12 European countries using a harmonized surveillance methodology. Because of the use of a consistent data collection protocol, it is possible to perform valid multiple comparisons between countries. It demonstrates wide variations in overweight and obesity prevalence estimates among primary-school children between European countries and regions. BACKGROUND: Nutritional surveillance in school-age children, using measured weight and height, is not common in the European Region of the World Health Organization (WHO). The WHO Regional Office for Europe has therefore initiated the WHO European Childhood Obesity Surveillance Initiative. OBJECTIVE: To present the anthropometric results of data collected in 2007/2008 and to investigate whether there exist differences across countries and between the sexes. METHODS: Weight and height were measured in 6-9-year-old children in 12 countries. Prevalence of overweight, obesity, stunting, thinness and underweight as well as mean Z-scores of anthropometric indices of height, weight and body mass index were calculated. RESULTS: A total of 168 832 children were included in the analyses and a school participation rate of more than 95% was obtained in 8 out of 12 countries. Stunting, underweight and thinness were rarely prevalent. However, 19.3-49.0% of boys and 18.4-42.5% of girls were overweight (including obesity and based on the 2007 WHO growth reference).The prevalence of obesity ranged from 6.0 to 26.6% among boys and from 4.6 to 17.3% among girls. Multi-country comparisons suggest the presence of a north-south gradient with the highest level of overweight found in southern European countries. CONCLUSIONS: Overweight among 6-9-year-old children is a serious public health concern and its variation across the European Region highly depends on the country. Comparable monitoring of child growth is possible across Europe and should be emphasized in national policies and implemented as part of action plans.