The article reports data from the WHO cross-national study on health behaviour in schoolchildren. A sample of 11,774 children aged 11, 13 and 15 years in Denmark, Finland, Norway and Sweden answered a questionnaire on social situation, health, health behaviour and lifestyle. Self assessed health is reported excellent among approximately two thirds of the Swedish children, half the Danish children, one third of the Finnish children and one fifth of the Norwegian children. In Denmark, Norway and Sweden self-assessed health is better among boys than girls. The most frequent symptom reported by the children is feeling low. Approximately half the children have experienced this condition at least once during the last week. Difficulties in getting to sleep, head ache, and feeling nervous are symptoms experienced by approximately one third of the children at least once a week. Smaller proportions of the children have experienced stomach-ache, back pain, bad temper and feeling dizzy. There are minor variations between countries and between age groups, but in almost all age groups in all countries more girls than boys report these symptoms. Approximately every fourth pupil have used medication against headache, stomach-ache and coughs during the last month. More girls than boys have used these medications, less pupils in Denmark than in the other countries. Very small proportions have used medication against nervousness and difficulties to getting to sleep.