Stroke is a major cause of death and disability, commonly caused by blood clots blocking large or small blood vessels of the brain. About one in five strokes are caused by disruption of blood flow in small vessels causing a lacunar stroke. This arises from diseased or hardened small blood vessels, known as small vessel disease (SVD). It can also cause widespread damage with loss of brain tissue structure, called leukoaraiosis. Lacunar stroke and leukoaraiosis is the most common cause of vascular dementia and a major cause of declining memory and thinking abilities that occurs with normal ageing. SVD is particularly common in individuals of African and African-Caribbean ancestry. It is not known why some people acquire SVD or what exactly causes it. Evidence suggests that genetic or inherited factors are important in increasing risk. However, the culprit genes have not yet been identified. New technology allows us to screen the whole of our genetic material to identify new genes causing diseases. We will examine brain scans and blood samples from stroke sufferers to try and identify genes associated with SVD in both White and Black stroke sufferers. Discovering new genes could lead to new treatments in this important disease.