Alzheimer's disease (AD) is a neurological disorder and the most common cause of dementia. One of the major pathological hallmarks of AD is the deposition of amyloid beta peptide (Aβ) into plaques. In the past decade, Positron Emission Tomography (PET) has been used to detect plaques in patients for diagnosis. Although several PET tracers including Flutemetamol (GE-067) have been developed and approved by FDA, their interaction with Aβ fibrils at molecular level is not fully understood. In this study, we aim to characterize the binding of GE-067 to Aβ1-40 fibrils in detail. We developed a binding assay based on HPLC quantification. Using Aβ1-40 fibrils prepared in vitro, we determined the binding stoichiometry of 1:4.6 (GE-067 to Aβ1-40 as a monomer). In collaboration with Prof. Hong, solid-state NMR and molecular docking were used to determine the binding sites of flutemetamol using , -labeled Aβ1-40. Our data support multiple binding sites for flutemetamol in Aβ1-40 fibrils. We believe our binding study will guide the effort to further optimize these amyloid PET tracers for higher affinity and selectivity.