There are many people who experience headaches that are independent of illness, injury, or hangover. Approximately 4% of the population suffer from headaches on a daily or near-daily basis. It is apparent that patients with chronic daily headache in community samples differ in important ways from patients with chronic daily headache in subspecialty clinics. In this manuscript, we review clinic-based data on risk factors for chronic daily headache and summarize the current data on the epidemiology of chronic daily headache.