OBJECTIVE To describe the association between status and change of neuropsychological function and postmortem neuropathologic findings in subjects with Alzheimer's disease, vascular dementia, normal aging, and pathologic aging. DESIGN Volunteer cohort study. SETTING Volunteers were interviewed and tested in outpatient-clinical research offices. PARTICIPANTS Nondemented, healthy, community-residing subjects, initially between 75 and 85 years of age, who participated in the Bronx Aging Study and had at least 2 years of neuropsychological data and quantitative neuropathologic examinations. MAIN OUTCOME MEASURES Initial summary neuropsychological score, rate of change score. RESULTS Summary neuropsychological scores at baseline in subjects who subsequently developed pathologically confirmed Alzheimer's disease or vascular dementia were 0.8 z units lower than those of subjects classified in the normal or pathologic aging subgroups (P < .05). Subjects with Alzheimer's disease showed more neuropsychological change over time than subjects in the normal or pathologic aging groups (P < .001). Normal subjects and subjects with pathologic aging did not differ in baseline scores or rate of change. Level of education was strongly associated with initial neuropsychological scores (P < .004), but not with change scores. CONCLUSIONS Among elderly, initially nondemented subjects who were followed up until death, subjects with pathologically confirmed Alzheimer's disease or vascular dementia had lower neuropsychological scores at initial evaluation than normal subjects or subjects with pathologic aging. Subjects with Alzheimer's disease had a more rapid rate of decline than normal subjects or subjects with pathologic aging.