Baskground There have been no large-scale international comparisons on bullying and health among adolescents. This study examined the association between bullying and physical and psychological symptoms among adolescents in 28 countries.Methods: This international cross-sectional survey included 123,227 students 11, 13 and 15 years of age from a nationally representative sample of schools in 28 countries in Europe and North America in 1997-98.The main outcome measures were physical and psychological symptoms.Results: The proportion of students being bullied varied enormously across countries. The lowest prevalence was observed among girls in Sweden (6.3%, 95% Cl: 5.2-7.4), the highest among boys in Lithuania (41.4%, 95% Cl 39.4-43.5). The risk of high symptom load increased with increasing exposure to bullying in all countries. In pooled analyses, with sex stratified multilevel logistic models adjusted for age, family affluence and country the odds ratios for symptoms among students who were bullied weekly ranged from 1.83 (95% Cl 1.70-1.97) to 2.11 (95% Cl 1.95-2.29) for physical symptoms (headache, stomach ache, backache, dizziness) and from 1.67 (95% Cl 1.55-1.78) to 7.47 (95% Cl 6.87-8.13) for psychological symptoms (bad temper, feeling nervous, feeling low, difficulties in getting to sleep, morning tiredness, feeling left out, loneliness, helplessness).Conclusion: There was a consistent, strong and graded association between bullying and each of 12 physical and psychological symptoms among adolescents in all 28 countries.