The goal of this proposal is to establish a population based registry of patients with Alzheimer's type dementia (DAT) and other dementias and to collect epidemiologic, genetic (pedigree), and clinical information for the investigation of etiologic factors related to DAT. Group Health Cooperative (GHC) central membership (approx. 25,000 over age 60) will form the population base. Incident cases of probable dementia presenting to GHC facilities will be identified, screened, and diagnostically evaluated. Approximately 150 of the projected 230 new dementia cases occurring yearly are expected to DAT. Since the registry is population based, incidence rates can be calculated. Sensitivity and specificity of the screening device will be evaluated; eventually accuracy of the clinical diagnosis also will be evaluable because neuropathologic data will be collected for validation of the clinical diagnosis of DAT. This registry will serve as the primary resource for future population based studies of the etiology of DAT and other types of dementia in conjunction with the University of Washington Alzheimer's Disease Research Center.