A veritable explosion of research in neuropsychology has occurred over the past decade in the search for cognitive and brain changes during a so-called “preclinical” phase of dementia that precedes its overt clinical manifestations. Fueling this explosion, in part, has been the revolution in the genetic bases of disease formulated from the international work of decoding the human genome (International Human Genome Sequencing Consortium, 2001; see also Patenaude et al., 2002, for discussion). The discovery of preclinical cognitive, brain, and genetic markers of dementia is helping to push back the point at which diseases can be reliably identified. Very early detection of dementia is extremely important now that a variety of investigational treatments that might prevent or delay disease progression (e.g., amyloid vaccine, anti-oxidants, nonsteroidal anti-inflammatory agents, cholinesterase inhibitors, estrogens, and others in the case of Alzheimer's disease) are on the horizon.