Researchers around the world are collaborating in the largest head-to-head tau PET dataset and harmonization effort ever undertaken. The findings could lead to significant advances in the diagnosis and treatment of Alzheimer’s Disease. Drs. Tharick Pascoal (University of Pittsburgh) and Suzanne Baker (Lawrence Berkeley National Laboratory) conceptualized The HEAD Study in late 2020 under the mentorship of Drs. William Klunk (University of Pittsburgh) and William Jagust (Lawrence Berkeley National Laboratory). In 2021, The National Institute on Aging awarded a $41M, 5-year grant to fund the study. This study aims to collect tau PET with the two most commonly used tau PET tracers (Flortaucipir and MK-6240), along with amyloid PET, MRI, blood, and cognitive measures in 620 study participants across 8 academic centers (University of Pittsburgh, Lawrence Berkeley National Laboratory, Houston Methodist Research Institute, Washington University in St. Louis, Mayo Clinic Rochester, University of California San Francisco, Brown University, McGill University), both at baseline at longitudinally at 18 months.