This study assessed professional caregivers of persons with Alzheimer disease (AD) and non-caregivers' knowledge about aging and AD. Participants completed modified versions of the Alzheimer Disease Knowledge Test and the multiple-choice version of the Facts on Aging Quiz #1. Overall, knowledge levels about AD and aging were low. Caregivers were found to be more knowledgeable about AD than were noncaregivers (58% and 42% correct, respectively), but these groups did not differ on knowledge about aging (40% and 39% correct, respectively). The most common misconceptions and areas of ignorance on the two tests demonstrate that participants rely on age stereotypes. (Contains 2 tables.)