OBJECTIVES: The present study examines the prevalence of headache in early adolescents in 21 European and North-American countries and the role of perceived teacher unfairness in predicting this health complaint across different countries. METHODS: Data were taken from the "Health Behaviour in School-aged Children" study (HBSC), a World Health Organization cross-national survey on health behaviors in 11-, 13- and 15-year-old students. Headache and perceived teacher unfairness were measured through a self-administered questionnaire filled out by 115,212 adolescents. RESULTS: The overall prevalence of frequent headaches (at least once a week) was 28.8%, ranging from 18.9% in Slovenia to 49.4% in Israel. After adjusting for gender, grade, family affluence, school achievement, being bullied and lifestyles (drinking, smoking, eating and physical activity), teacher unfairness showed a significant association with frequent headache in all but two countries (Ukraine and Luxembourg). CONCLUSIONS: Our results show that headache is a common health symptom in European and North-American countries, even though there are substantial differences in its prevalence across countries. The study indicates that perceived teacher unfairness can be a significant predictor of frequent headache during adolescence, and this association is consistent across countries.