Neuroimaging tools have been used for more than two decades in a variety of investigations on Alzheimer’s disease (AD). Quantitative in vivo measures of brain structure, function, chemistry, and pathology and other features have been shown to be abnormal in patients with AD. Recently, a number of these measures have been proposed as potential imaging biomarkers for various purposes in AD. These studies, reviewed here, provide a variety of illustrative examples of the uses of imaging markers in drug development that are applicable to other neuropsychiatric disorders.