Patients with transient global amnesia are often categorized as having cerebrovascular disease. Noninvasive carotid artery testing was performed in 56 patients with transient global amnesia to determine if they had the same incidence of extracranial atherosclerotic vascular disease as patients with focal cerebral transient ischemic attacks. Only 3 of 56 patients had hemodynamic obstruction of flow at the carotid artery bifurcation, and 41 of 56 had no evidence of any atherosclerotic disease. Other risk factors for cerebrovascular disease were present in 24 of 56 patients, but only 1 had a prior cerebrovascular event. The pathophysiology of transient global amnesia appears to differ from the pathophysiology of classical transient ischemic attacks in that there is no clear relation between transient global amnesia and the presence of extracranial atherosclerotic cerebrovascular disease.