Early diagnosis of presenile Alzheimer's disease (AD), which would serve for prognosis and for guiding choices of treatment, is still an important, difficult task for the clinical neurologist. We studied 24 patients, 12 of whom had minor cognitive impairment or questionable dementia (PICD) and 12 who met NINCDS-ADRDA criteria for presenile AD (PAD). Using clinical, neuropsychological, neurophysiological and neuroradiological methods, we followed the patients up to two disease end-points: death or untestable condition. This paper concentrates on the main clinical and neuropsychological findings relative to these two end-points. All PAD patients evolved into clinically evident Alzheimer-type dementia, became untestable within 60 months and died within 72 months. Only 3 of the PICD patients became demented; 2 of them died during the follow-up and 1 died eight months later. The other 9 PICD patients showed only moderate cognitive decline, compatible with normal aging processes. Neurophysiological and neuroradiological findings might be an important tool for arriving at a correct early diagnosis, when they are assessed with clinical neuropsychological data.