The present study dealt with the prevalence of headache generally and migraine in particular among school children. The sample consisted of a total of 3,784 school children, accounting for 94.5% of all grade school pupils aged 13 in two Finnish cities, Tampere and Turku. The data were obtained by use of a questionnaire, filled in by the pupils according to instructions under the supervision of the class's homeroom teacher during class. Headache had occurred during 1980 in 82% of the pupils. In about one-half (53%) of the pupils it had occurred less than once a month. It occurred monthly in 9% and weekly in 8%. Frequent headache was more common in girls than in boys and was also more commonly paroxysmal in character. Boys had had headaches more often before 1980 than during 1980, whereas in girls headaches had become more common in 1980 than before. Migraine was found to occur for 11.3% of the pupils. It was more common in girls (14.5%) than in boys (8.1%). Classic migraine, in particular, occurred more often in girls. Migraine had ceased to occur prior to 1980 in 24% of cases. In particular those attacks which involved a family history of migraine, visual aura or nausea and/or vomiting had ceased to occur. Migraine too had more commonly ceased to occur in boys (23.3%) than in girls (15.1%). Comparison with previous research showed that the occurrence of migraine had more than doubled during 25 years.