The rarest kind of Alzheimer's disease, the form that is inherited from parent to child with a cruel 50 percent likelihood, has long been marked by its untapped opportunities. Affected families have made possible both the discovery of the first three Alzheimer’s genes and the elaboration of the amyloid hypothesis. Beyond that, these families have much more to give to research, and gain from it, because the preclinical phase of AD can be studied and targeted for prevention in still-healthy carriers who are certain to develop AD in the future. This has been difficult to do because these families are rare and live all across the globe. Now, an international registry called Dominantly Inherited Alzheimer’s Network (DIAN) is preparing to fill the gap. Starting in January 2009, this 10-center, publicly funded consortium will open its doors for adult children of eFAD families. Carriers, non-carriers, and those who do not want to know their genetic status are welcome to join a comprehensive study that aims to pave the way for future prevention trials.