The authors reviewed 30 studies on Alzheimer's disease to determine the prevalence and phenomenology of affective and psychotic symptoms in patients with this disorder. Depressive and psychotic symptoms occurred in 30%-40% of the Alzheimer's disease patients. Isolated symptoms were two to three times as frequent as diagnosable affective or psychotic disorders. Paranoid delusions were the most common psychotic symptoms reported. Implications of the relationship of psychiatric symptoms to the clinical presentation of Alzheimer's disease, patterns of cognitive dysfunction, clinical management, and areas for future research are discussed.