Patients with chronic daily headaches are commonly encountered in headache specialty centers but their clinical characteristics have rarely been documented. We studied 100 consecutive patients with chronic daily headache to determine their presenting characteristics and other associated features. Half of the patients described their headache as a steady ache but throbbing pain was reported in about one third. About half estimated the degree of pain as moderate but one third claimed the typical pain was severe. A consistently unilateral site was noted in only 2 percent. Associated features characteristic of migraine were often noted: Including photophobia (37 percent), photophobia (42 percent), and nausea (24 percent). Many also reported aggravating and ameliorating factors commonly associated with migraine. We conclude that the manifestations of chronic daily headache are extremely diverse, probably reflecting the heterogeneous mechanisms which underlie this condition.