There is an unusual type of vascular episode in the territory of the posterior cerebral artery which remains relatively unknown. Ten cases are presented in which a posterior cerebral artery deficit developed suddenly in dramatic fashion with headache, visual symptoms, sensory and motor deficits and signs of third nerve involvement. Nine of the patients were female and one was male. Seven were under the age of 33. In all instances there was a permanent neurologic sequela, usually a hemianopia. A similar case was described in 1901. The nature of the underlying process remains obscure, but the evidence favors accompanied migraine in which a particularly severe attack results in permanent damage. The term “catastrophic migraine” is suggested.