It is generally thought that public understanding of science is inadequate. The definitions of "the public," "understanding," and "science" all need careful consideration in this formulation, with a greater focus on who should understand what and for what purposes. Improved public understanding depends on experts being reflective about the limits of their own expertise and the different needs of the many potential consumers of genetic knowledge. Media coverage of genetic discoveries has been extensive in recent years, but this coverage is often not useful and may even be misleading to families at risk for genetic disease. The Internet provides an alternative source of information as well as an interactive forum, one that has been widely used by persons interested in Alzheimer disease (AD). Internet-based activities hold great promise for providing interested members of the public with useful information and facilitating more substantive dialogue among physicians, researches, and laypersons regarding the genetic aspects of AD.