Ehlers-Danlos syndrome (EDS) type IV is an autosomal dominant disorder that results from mutations in the COL3A1 gene, which encodes chains of type III procollagen. Individuals with this disorder are predisposed to rupture of arteries, the bowel, and the gravid uterus. To assess the frequency of central nervous system complications, we reviewed clinical data concerning 202 individuals with EDS type IV from 121 families in which the diagnosis was confirmed by biochemical or molecular studies. We identified 19 individuals with cerebrovascular complications, which included intracranial aneurysms with secondary hemorrhage, spontaneous carotid-cavernous sinus fistula, and cercical artery dissection. The mean age at presentation with these events was 28.3 years (range, 17-48 years). Although uncommon, EDS type IV is an important potential cause of stroke in young people. The disorder is readily identifiable clinically and the diagnosis has important implications for acute and long-term management and, potentially, for other family members. Because conventional angiography may exacerbate severe complications, noninvasive procedures such as Doppler and magnetic resonance angiography are the investigations of choice. Anticoagulation therapy may result in increased bruising or bleeding and should be used with caution.