Amyloid beta (A-beta) is the proposed causative agent of Alzheimer's disease (AD) as accumulation of A-beta in senile plaques is one of the neuropathological hallmarks of AD. A-beta is continuously being made and secreted from cells. Extracellular A-beta is cleared from the brain by a variety of mechanisms including proteolytic degradation and transport across the blood-brain barrier. Research is showing that a failure to eliminate extracellular A-beta plays an important role in the pathogenesis of AD as deposition of A-beta is seen in individuals years before they show the characteristic symptoms of AD. R&D Systems offers a range of research tools needed for investigating the mechanisms of A-beta clearance.