[en] It is well known that the number of the neuron in the brain gradually reduced with advancing age, but speed of decline of brain functions differs among individuals. We have reported that social environmental factors had significant influences to cerebral blood flow (CBF) and mental function. In this paper, we report 2.5 years longitudinal study concerning with CBF and intelligences in twenty normal elderly people, mean age of 76 years old at the first measurement, living in retirement house. 1) Mean CBF measured by Xe 133 inhalation method did not alter significantly during the observation period. 2) Performance intelligence evaluated by Kohs' block design test had reduced at the point of begining but no more reduction was observed during the period. 3) Verbal intelligence evaluated by Hasegawa's intelligence scale for aged which was within normal range at the begining, slightly (-7.5 %) but significantly (p < 0.05) reduced during the period. 4) Performance intelligence tended to reduce in subjects who showed reduction of CBF. There were no significant correlation between both intelligences and CBF. CBF could be maintained even in elderly people living in retirement house which has less social stimuli during relatively short observation period in so far as they maintain active daily life. The speed of reduction of performance intelligence may be getting slow after certain age and verbal intelligence gradually decreases perhaps by disuse of the mental function. (author)