Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common genetic disorder among those responsible for hereditary strokes, and it is caused by a mutation in the NOTCH3 gene on chromosome 19. The gene discussed is NOTCH3; the disease is cerebral arteriopathy with subcortical infarcts and leukoencephalopathy.