Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a heritable small-vessel disease caused by mutations in NOTCH3 gene and clinically characterized by recurrent ischemic strokes, migraine with aura, psychiatric symptoms, cognitive decline and dementia. Direct sequencing of NOTCH3 gene in 90 Italian patients of sixty-three unrelated families identified four heterozygous mutations (R141C and C144F in exon 4, G528C in exon 10 and R1006C in exon 19) in fifteen probands and sixteen relatives. We detected seventeen heterozygous/homozygous polymorphisms, four of them novel. Here we report the high recurrence of R1006C mutation in ten families all originate from a restricted area of central Italy, the town of Ascoli Piceno and same neighbour villages. We also developed a PCR-Restriction Fragment Length Polymorphism (RFLP) assay to analyze the R1006C mutation. Our findings might suggest, for this mutation, the presence of a common ancestor.