Migraine epidemiology presents methodological challenges, partially simplified by the use of the new International Headache Society (IHS) Classification. Most previously published migraine studies were clinic-based, which introduces bias since less than 5% of migraineurs consult specialists. A series of population-based studies of migraine prevalence and incidence, based on the new operational IHS criteria, are now available and are reviewed, along with the migraine personality, comorbid psychiatric conditions and neuropsychological impairment. Migraine headaches are now divided into those with aura (classic migraine) and those without aura (common migraine). Headache occurs in about 91% of men and 96% of women, migraine occurs in about 6% of men and 18% of women (one-year prevalence). Migraine is most common in the third decade of life and in lower socioeconomic groups. It is associated with an increased prevalence of depression and panic attacks.