This study was carried out to define the effects of both long-term hypertension and hypotension on the cerebral functioning of the elderly, comparing them to the effects of normotension. Ninety-eight subjects of both sexes, between 70 and 82 years of age, were divided into three groups on the basis of their mean blood pressure: 33 normotensives, 36 hypotensives and 29 hypertensives. They underwent a neuropsychological assessment, a haemorrheological evaluation and an EEG monitoring while awake. The results show that the three parameters were almost always within normal limits in the normotensives, while EEG alterations, lower neurophysiological scores and blood hyperviscosity were noted in both the hypertensives and hypotensives. Our results would seem to confirm that long-term hypertension may induce alterations in the cerebral electrogenesis and intellectual functions of the elderly and that also long-term hypotension might negatively interfere with some functional aspects of the aging brain.