SNMMI and the Alzheimer’s Association and their designated experts, collaborated to update this Appropriate Use Criteria (AUC) document. The primary goal of this AUC is to assist clinicians in identifying clinical scenarios in which amyloid or tau PET may be useful for guiding the diagnosis and management of patients who have, or are at risk for, cognitive decline, while also highlighting scenarios in which PET scans are unlikely to provide clinically useful information. This is an update of the original AUC which was published in 2013 and it includes tau imaging and up-to-date use cases for amyloid in light of the disease modifying agents.