text: In an initial longitudinal study 164 of 176 subjects 60 to 84 years of age were followed. Of these 136 subjects with normal aging or AD at baseline were followed over a mean interval of 3.5 plus or minus 0.6 years; and 28 subjects with normal aging or dementia and vascular disease at baseline were followed over a mean interval of 3.8 plus or minus 0.6 years. Additionally, we have evaluated at baseline 198 and 112 subjects from the two group non-vascular and vascular), who are now due for their initial follow-up. Tentative operational definitions of the boundaries between normal aging and AD have been suggested by our present data. Information has also accrued about the course of AD and of dementia with vascular concomitants. These findings need to be confirmed and expanded upon. We now propose to follow-up the previously studied and followed cohorts after a further 5 year interval (N=164). Simultaneously, we propose to complete an initial follow-up on more recently studied subjects (N=310). We will follow the more severe subjects (presently 139 subjects with non-vascular and vascular dementia) annually, conducting home visits and nursing home visits when necessary. Post-mortem studies will continue to be conducted whenever possible. The goals are to confirm and extent the findings of our initial studies and to investigate the hypotheses raised by our findings to date. The ability to counsel patients and families of AD victims with respect to prognosis at all stages of the illness and to differentiate the borders of aging AD should be further improved.