Migraine is a chronic and sometimes progressive disorder characterized by recurrent episodes of headache and associated symptoms. This article reviews the epidemiology of and the risk factors for migraine described in population studies, and discusses the burden of disease and the socioeconomic costs of migraine. In the years prior to puberty, migraine is more common among boys than girls. By the onset of puberty, migraine is more prevalent in girls, and by the late teens, females are about twice as likely to suffer from migraine as males. The prevalence of migraine peaks in both sexes during the most productive years of adulthood (age 25 to 55 years) and, in the United States, the prevalence is higher in individuals of lower socioeconomic status. Direct costs of migraine include the cost of migraine medications and health care expenses. Indirect costs associated with migraine include reduced productivity due to absenteeism and reduced performance while at work. Recent evidence suggests that a subgroup of migraine patients may have a clinically progressive disorder. Future epidemiologic studies should focus on identifying patients who are at higher risk for progression and on assessing the impact of intervention strategies on disease progression.