Migraine is a very common phenomenon. Eighteen percent of women in this country and 6% of men have migraine. The old classification for headaches and diagnostic criteria were published in 1962, more than a quarter of a century ago. In 1988, the International Headache Society published a new classification and diagnostic criteria for all headache disorders, cranial neuralgias, and facial pain. The International Headache Society classification divides migraine, as it had been divided in the past, into two major categories: migraine without aura (formerly called common migraine) and migraine with aura (formerly called classical migraine). These criteria are rather complex and simpler criteria are proposed for clinical practice. The typical patient with migraine is a woman whose headaches began in adolescence or young adult life. There usually is a family history of migraine. Migraine is almost always more than just a headache. Virtually anything in the external environment and many things in the internal milieu may provoke migraine in a susceptible individual. There are many potential manifestations of the aura of migraine, but 90% are visual phenomena. Migraine in children is a little different than in adults. When the onset is below the age of puberty, the ratio of females to males is equal, but after puberty there is a striking predominance of women over men in a ratio of 3:1. Whenever the history of migraine is not typical or if something unexpected is found on examination, imaging studies are warranted.