Behavioral abnormalities and psychiatric symptoms were assessed in 178 patients diagnosed as having Alzheimer's disease by NINCDS/ADRDA criteria. The subjects were selected from a defined catchment area and therefore were representative of a group of patients with Alzheimer's disease of varying severity. Auditory hallucinations were found in 10%, visual hallucinations in 13%, and delusions in 16%. Symptoms suggestive of depression were reported by 39% of the patients and features of depression observed in 25%. Twenty percent were aggressive, and 7% were sexually disinhibited. Nineteen percent exhibited excessive walking behavior and 10% binge eating. Nearly 50% of the sample were incontinent. Patients in the hospital were more often aggressive, incontinent, and seemingly less depressed. Patients with severe dementia displayed excessive walking behavior, were more likely to be incontinent, and reported less depressive symptoms than those with moderate or mild dementia.