Transient ischemic attacks (TIA) are episodes of abrupt beginning, consisting of subjective or objective neurological dysfunction of short duration, with complete recovery of neurological function in the course of 24 hours. With this definition, the authors carried out a retrospective study of 150 patients suffering from ischemic infarct in the brain in the territory of the middle cerebral artery. Thirty-eight percent of the patients had had TIAs before their cerebral infarct. The symptoms, in order of frequency, were motor, sensory deficits, alterations of speech and vision. Most of the patients had a definite cerebral infarct, occurring one month after the last TIA; the symptoms of both processes were remarkably similar. The authors studied the angiographic characteristics, pharmacological and toxic antecedents, and associated diseases in these patients. The study indicates that TIA may be the first manifestation of cerebral vascular disease.