P300 latency and amplitude were investigated in 10 normal elderly individuals, 10 institutionalized elderly persons with dementia not of the Alzheimer's types, and 10 elderly people with Alzheimer's disease. Significant differences between control and dementia groups (but not between dementia groups) were noted in the P300 latency, but not amplitude. Such differential latencies were observed in the anterior and in the left temporal and parietal areas of the brain.