We studied headache features in 3,126 patients with acute cerebral or retinal ischemia. Headache occurred in 18% of these patients (in 16% of all patients with transient ischemic attacks, in 18% of patients with reversible ischemic neurologic deficits, and in 19% of patients with minor strokes) and was mostly continuous in all types of attacks. Headache was present in 16% of patients with monocular visual symptoms. The occurrence of headache was not related to the mode of onset, mode of disappearance, or duration of the attack. Patients with headache more often were known to have heart disease. Headache was less frequent in patients with small deep infarcts, who were more often hypertensive, and in patients with infarcts in the anterior circulation; headache was more frequent in patients with cortical infarcts and in patients with infarcts in the posterior circulation. Patients with a relevant small deep infarct on computed tomographic scan and accompanying headache relatively often reported symptoms compatible with cortical ischemia, such as language disorders or a visual field defect. We conclude that headache is a frequent accompanying symptom in patients with acute cerebral and retinal ischemia and that the occurrence of headache is partly related to the underlying cause of the ischemic lesion.