The ability to diagnose the pathology of neurodegenerative diseases in patients during life remains one of the holy grails of behavioral neurology. Considerable progress has been made over the past decade or so. We can now accurately predict the pathology—Alzheimer disease (AD) with plaques and tangles—in patients with progressive amnesia accompanied by attentional and executive deficits and followed, in turn, by aphasic and visuospatial problems. The accuracy of AD diagnoses has also been aided by the advent of ligand-based amyloid positron emission tomographic imaging, although this technique remains extremely expensive and is only available in the developing world and, even there, is not yet available in clinical practice.