Positive neuropsychiatric features (paranoia, delusions, hallucinations) and negative features (disinterest/withdrawal, apathy, reduced speech output, reduced physical activity) occur in Alzheimer's disease (AD), although most studies have focused on positive features alone. Positive features may be associated with a more severe and rapidly progressive subtype of AD. A retrospective analysis of prospectively obtained research data (101 probable AD patients) revealed that patients with positive features had been ill longer but were otherwise similar to patients with negative features. Patients with any neuropsychiatric features had more rapid progression and more severe cognitive and comprehension deficits than patients without such features. Neuropsychiatric features in AD likely reflect variations in mesocortical and mesolimbic degeneration rather than an etiologic or prognostic subtype.