This study examines whether cognitive markers at prior examinations are indicative of subsequent dementia and mortality. The sample was composed of subjects aged 84-90 at baseline who were reexamined three times over a 6-year period on a comprehensive biobehavioral battery. Dementia was evaluated at each examination using DSM-III-R criteria. Results indicated that incident cases of dementia had lower cognitive scores both 2 and 4 years prior to diagnosis, compared to non-demented survivors. Evidence for terminal decline was also found, as people who subsequently died also had lower cognitive performance at prior examinations, compared to non-demented survivors. The findings suggest that mild cognitive dysfunction is an important clinical finding among the oldest old and may herald either the onset of dementia or mortality.