In a survey conducted by a UK urban general practice, 98.1 per cent (1083) of the children registered aged three to 11 years took part in an interview. Possible migraine subjects took part in an extended interview, the results of which were recorded using three different sets of diagnostic criteria: Vahlquist, Ad Hoc and International Headache Society. The prevalence of migraine ranged from 3.7 to 4.9 per cent, depending on the criteria used. The prevalence of migraine with aura (1.5 per cent) was similar by all criteria, whereas that for migraine without aura ranged from 2.2 to 3.4 per cent. The prevalence of migraine increased with age. The IHS criteria appeared less sensitive than the Ad Hoc for migraine without aura. Operational criteria using three attacks lasting longer than one hour may be more specific for the diagnosis of migraine in young children.