Impairments with the blood vessels in the brain are common in Alzheimer’s disease and are thought to contribute to cognitive decline. This proposal seeks to further understand the blood-based system called the contact system and its role in Alzheimer’s disease. The contact system is involved in blood clotting and inflammation, and is activated in patients with Alzheimer’s disease. It is thought that the contact system contributes to disease pathology in mouse models of Alzheimer’s. A better understanding of the contact system has the potential to improve diagnosis in patients with vascular contributors to dementia. In addition, this proposal seeks to explore the potential of targeting the contact system as a novel treatment strategy.