Cognitive and noncognitive psychiatric symptoms were systematically evaluated in 21 patients with Alzheimer's disease by using the Neurobehavioral Rating Scale. Regional cerebral metabolic activity was measured in each patient by [18F]fluorodeoxyglucose PET. Significant correlations emerged between global cortical metabolic activity and the Agitation/Disinhibition factor score, Cognition factor score, and total score. Relationships between noncognitive symptoms and metabolic activity were regionally specific, with significant correlations between Agitation/Disinhibition factor score and metabolism in the frontal and temporal lobes, between Psychosis factor score and metabolism in the frontal lobe, and between Anxiety/Depression factor score and metabolism in the parietal lobe. These results suggest that psychiatric symptoms are fundamental expressions of the cortical dysfunction of Alzheimer's disease.