We conducted full diagnostic evaluations, including a comprehensive cognitive assessment battery, of a group of 32 elderly subjects with a clinically identified mild cognitive impairment and a group of 32 age-matched and education-matched normal subjects. The mildly impaired subjects performed significantly more poorly than the controls on tests of recent memory, remote memory, language function, concept formation, and visuospatial praxis. Follow-up evaluations of cognitive status 2 years later revealed clinically detectable cognitive decline relative baseline in 23 (72%) of the mildly impaired subjects. Several of the objective psychological tests accurately discriminated at baseline between the decliners and nondecliners in the mildly impaired group. Among the 20 mildly impaired subjects with no complicating conditions, 16 exhibited cognitive deterioration between baseline and follow-up. These results suggest that most elderly subjects with mild cognitive deficits, as determined by clinical evaluation and objective psychological testing, will manifest the progressive mental deterioration characteristic of dementia and that psychometric predictors can be used to distinguish between benign and more significant underlying disorders in mildly impaired elderly subjects.