Chromosome examinations in 94 aging women from a variety of institutional settings were compared with those of 15 young and 12 middle-aged women. The percentage of peripheral leukocytes which, after 72 hours in culture, showed loss of one or more chromosomes (hypodiploid cells) was larger among the aged than among the middle-aged or young women. Most of the missing chromosomes belonged to the C-group, but since this work was completed before the banding techniques came into use, unequivocal identification of the X chromosome was not carried out. Using type of residence as an indirect measure of mental status, the data provide confirmation for a previously hypothesized association between mental status and chromosome loss in the aged.