The screening protocol is designed to evaluate volunteers/patients for participation in IRB approved clinical studies of the National Institute on Aging (NIA). An additional purpose of this protocol is to develop a registry of individuals who have been evaluated through the NIA Clinical Research Unit screening clinic. To participate, volunteers/patients must meet the specific requirements of at least one of the available NIA research studies. This protocol serves as a first step for admitting volunteers/patients to an appropriate approved protocol, and it is used to develop a registry of individuals who meet eligibility criteria for existing research projects.