We studied the characteristics of headaches in 161 consecutive symptomatic patients with spontaneous dissections of the internal carotid artery (n = 135) or the vertebral artery (n = 26). For patients with internal carotid artery dissection (ICAD), the mean age was 47 years and for those with vertebral artery dissection (VAD), 40.7 years. A history of migraine was present in 18% of the ICAD group and in 23% of the VAD group. Headache was reported by 68% of the patients with ICAD and by 69% of those with VAD, and, when present, it was the initial manifestation in 47% of those with ICAD and in 33% of those with VAD. Ten percent of patients with ICAD had eye, facial, or ear pain without headache. The median interval from onset of headache to development of other neurologic manifestations was 4 days for the ICAD group and 14.5 hours for the VAD group. For all dissections, headaches typically were ipsilateral to the side of dissection. In the ICAD group, headaches were limited to the anterior head in 60% of patients and were steady in 73% and pulsating in 25%. In the VAD group, headaches were distributed posteriorly in 83% of patients and were steady in 56% and pulsating in 44%. Neck pain was present in 26% of patients with ICAD (anterolateral) and in 46% of those with VAD (posterior). The median duration of the headache in patients with VAD and ICAD was 72 hours, but headaches became prolonged, persisting for months to years, in four patients with ICAD.