In order to better understand the earliest signs of cognitive decline caused by Aizheimer's disease (AD) and other dementing illnesses, information is needed from well-characterized nondemented individuals studied longitudinally until autopsy. We studied the clinical and cognitive features associated with the development of AD or other dementias in nondemented older adults enrolled in a longitudinal study of memory and aging and who were followed to autopsy. Individuals who remained nondemented showed stable cognitive performance. In those individuals who eventually developed dementia minimal cognitive decline occurred prior to dementia diagnosis, after which sharp decline was noted. Predictors of eventual dementia included older age, deficits in judgment and problem solving skills as well as memory, slowed psychomotor performance, and depressive features. In a subset of nondemented individuals, histopathologic AD was present at autopsy suggesting a preclinical state. Further evaluation of these individuals demonstrated an absence of practice effects on cognitive testing.