Aß (θ-amyloid peptide) is a major component of neuritic plaques and cerebrovascular amyloid deposits in the brains of patients with Alzheimer’s disease (AD). The cellular origin of amyloid precursor protein (APP) that give rise to AΒ is now well understood. Morphological evidence suggests that APP-immunoreactive neurites, often capped by Aß deposits are one the major source of parenchymal amyloid. However, others cells, including astroglia, microglia, and vascular cells, may contribute to the formation of Aβ. A long-standing hypothesis has been that Aß deposits are neurotoxic and are causative factors in the development and progression of AD. Hence, development of inhibitors of Aß fibrillogenesis has become an important area of research.