Cerebral blood flow was measured by the 133Xenon washout method in 44 cognitively intact subjects. Regression analysis of cerebral blood flow with age was performed on data from 33 subjects without arteriosclerotic cardiovascular disease, hypertension, or chronic obstructive pulmonary disease, factors which have been previously shown to lower cerebral blood flow. Changes with normal aging were significant in the left and right hemispheres with bilateral changes in temporal, parietal, and occipital regions. An additional group of 11 cognitively intact subjects with arteriosclerotic cardiovascular disease but no accompanying dementing disease had lower mean flow values at each detector position than did age- and sex-matched controls, although the differences did not always reach statistical significance. Decreased flows in temporal regions seem to be a concomitant of normal aging, and are not related to the presence of vascular disease.