Reports of increased prevalence of headache in adults and clinical impressions of similar trends in children prompted this epidemiological study on migraine and other headaches. The first stage was carried out in 1974 in children starting school, and the second stage in 1992 using the identical study design, the same age group, and a similar urban child population. The overall prevalence of present headache (having occurred in the previous 6 months) was found to be significantly increased over time, from 14.4% in 1974 to 51.5% in 1992. Similarly, the prevalence of migraine headache had increased from 1.9% to 5.7%. The causes of the increase are as yet unknown. The highest but not significant increases were found in schools which were situated in the districts of the city with the highest social instability, which was reflected in the high percentage of council houses and also in the higher frequency of family relocations. Increase over time in the prevalence of migraine and other headaches in children appears to be at least as clear as in adults. This should alarm the community to study the underlying stress factors and to try to relieve the children's distress.