Migraine is a very common disorder, affecting about 11% of adult populations in Western countries. Prevalence is highest during the peak productive years--between the ages of 25 and 55. The prevalence is higher in females than males at all post-pubertal ages, but the sex ratio varies with age. In the United States, migraine prevalence is higher in those with low income or education, perhaps because migraine interferes with work and school. Most migraineurs mane their headaches without conventional medical advice and generally treat their attacks with over-the-counter medication. The indirect costs of migraine greatly outweigh the cost of treatment, creating opportunities for cost-effective intervention. The public health burden of migraine is substantial due to its high prevalence and prominent temporary disability. The widespread disability produced by migraine is an important target for treatment.