Alzheimer disease (AD) is a multifaceted disorder with primary manifestations involving neuropsychologic, neuropsychiatric, and neurologic domains. These primary disturbances are based on brain dysfunction and produce secondary effects on patient activities of daily living and quality of life, and have adverse consequences for caregivers, family members, and society. Apathy, agitation, mood disturbances, irritability, disinhibition, delusions, aberrant motor behavior, and abnormalities of sleep and eating are common in AD. The neuropsychiatric disorders of AD are mediated by limbic system and frontal lobe dysfunction and are related in part to the cholinergic deficiency affecting these structures. Cholinomimetic therapy ameliorates the behavioral and emotional disturbances of AD. Cholinergic compounds are unique psychotropic agents that exhibit disease specificity, exerting beneficial effects only in diseases such as AD with cholinergic deficits. Cholinergic agents are potentially useful in the treatment of behavioral disturbances of AD, and their neuropsychiatric effects should be assessed in all clinical trials of these compounds.