The most common form of familial vascular dementia is considered to be CADASIL or cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, which is now also increasingly manifest in the United Kingdom. CADASIL has been previously dubbed as a familial form of Binswanger disease. However, unlike in Binswanger disease CADASIL does not involve hypertension or other risk factors associated with cardiovascular disease. CADASIL appears to be essentially a disorder of the arteries that is linked to single missense mutations in the NOTCH 3 gene locus on chromosome 19. The pathogenesis of the disorder or the genetic mechanism leading to brain infarcts and dementia is not known. The elucidation of the microvascular pathology evident in CADASIL may be an interesting way to delineate effects of defective genes on brain cells from systemic vascular influences.