In Western countries, recent community-based studies of migraine prevalence using standardized diagnostic criteria give 1-year prevalence estimates of around 10 to 12%. The prevalence of migraine is age- and gender-dependent. Age at onset of migraine is earlier in boys than in girls. Migraine is two to three times more common in women than in men, with peak prevalence occurring during mid-life in both sexes. Current evidence also indicates that migraine prevalence is higher in Caucasians than in Africans or Asians. In some migraineurs, attacks may be frequent or prolonged, leading to considerable pain and disability. There has been much debate over predisposing factors, which are not sufficient by themselves to cause an attack, as well as precipitants, which immediately precede the attack. However, convincing data are lacking for most of these. Significant associations have been reported between migraine and certain psychiatric disorders, epilepsy, and stroke in women under the age of 45. These findings demonstrate that migraine is common, has a substantial impact on sufferers, and may be associated with other disorders.