Alzheimer’s disease (AD) is the most common form of dementia in mid- to late life and one of the most serious health problems in the industrialized world. The elderly are the fastest growing part of the population, and increases in life expectancy will inevitably lead to a further increase in the prevalence of AD. Moreover, age-associated cognitive impairments affecting 10 times as many individuals. 1 The risk of developing AD doubles approximately every 5 years between the ages of 65 and 85 years, and as the baby boomer generation ages, it is estimated that in 30 years 15 to 20 million elderly nationwide may have some cognitive disability. 1, 2 The demographics of aging thus suggest a great need to diagnose AD accurately and distinguish it specifically from the many other possible causes of cognitive impairment. As strategies to delay disease progression and possibly prevent or offset the onset of AD are under development, 3 it is extremely important to recognize individuals at high risk for developing AD who may particularly benefit from early therapeutic interventions. Remarkable progress has been made in the understanding of the cascade of molecular events leading to AD. In the last decade, genetic abnormalities have been identified, new pathophysiologic mechanisms discovered, therapeutic agents approved, and diagnostic tests developed. Nonetheless, fundamental questions remain unanswered and the lack of specific biological markers hinders the management of AD. With the development of specific and effective prevention treatments, improved early detection of AD will be increasingly critical for medical care.