There are approximately 1.3 million cases of severe dementia in the United States affecting 5% to 15% of the population age 65 or older. Recent estimates suggest that 20-46% of the population may be affected by age 85. Alzheimer's Disease (AD) accounts for the largest proportion of cases of dementia in persons over the age of 65 years. Of the more common complications of AD, behavioral disturbances such as psychosis and agitation dramatically impact on the quality of life of the patient and caregiver. Psychosis develops in approximately one-third of patients with AD. AD patients who become psychotic often pose a threat to themselves and occasionally to others. Psychotic symptoms often require chronic neuroleptic treatment which may produce neuroleptic sensitivity syndrome and tardive dyskinesia. The management of psychosis and behavioral disturbances in AD often requires intensive care, greater follow-up, and sometimes institutionalization, all of which increase the economic burden of the illness. The ability to predict the development of psychosis or other behavioral disturbances such as agitation would influence the pharmacologic management of AD patients. Because of the many disabling side-effects of neuroleptics, any information delimiting their use would be clinically helpful. If it could be determined early that certain characteristics identify patients who are less likely to develop psychosis, and therefore less likely to require chronic neuroleptic treatment, then, should such patients develop behavioral problems, extra consideration could be given to the use of non-neuroleptic approaches. Also, the economic burden and perhaps the course of the illness could be more realistically estimated for a given patient. Although previous long-term prospective investigations have examined potential risk factors for clinical decline in AD, none has specifically examined risk factors for the development of psychosis or agitation. Because there is evidence from cross-sectional studies that suggests a relationship between EPS, neuropsychological and psychosocial disturbances and psychosis in AD, we considered that these measures, in various combinations, will predict the development and time course of psychosis in AD. The goal of the proposed research is to undertake a five-year prospective study of AD patients in order to identify important motor, neuropsychological, psychosocial and demographic factors related to the risk of developing neurobehavioral disturbances and the time course over which these disturbances develop.