Neurodegenerative diseases have neuropsychological, neuropsychiatric, and neurological effects manifested as cognitive, emotional, and physical alterations. These primary effects have secondary consequences on activities of daily living, patient and caregiver distress, and quality of life. Neuropsychiatric manifestations are products of brain dysfunction that are associated with institutionalization, vulnerability to abuse by the caregiver, and use of medications and restraints. Behavioral alterations can often be ameliorated by psychotropic drugs, and the effects of medications contribute to understanding the mechanisms of behavioral changes. Allocation of health service resources for dementia patients is partially determined by the neuropsychiatric dimension of these diseases, and the importance of the neuropsychiatric aspects of degenerative disorders has been underemphasized.