Background: Ehlers-Danlos syndrome type IV (EDS IV), the vascular type, is characterized by easy bruising, thin skin with visible veins, and spontaneous rupture of the large arteries, uterus, or bowel. Other vasculopathy involves the dissection or aneurysms of the aorta or large arteries, carotid-cavernous fistula (CCF), and intracranial aneurysms. EDS IV is caused by mutations in the gene for type III procollagen (COL3A1). Methods and Results: We retrospectively reviewed the clinical data of 6 probands (2 males and 4 females) with a clinical diagnosis of EDS-IV treated over a 10-year period (1998 – 2008). Genetic analysis was obtained in 6 patients, and mutation of the COL3A1 gene was confirmed in 5 patients. Pedigree history and molecular study of family members identified 3 patients. Total 7 patients from 6 families were analyzed. Of the 7 patients, only one had an established diagnosis before they presented at our institution. The mean age at the time of diagnosis was 30 +/- 13 years (range, 11 to 48 years). Five patients developed vascular complications. Acute rapidly extending dissection of the abdominal aorta, chronic focal dissected aneurysm of the abdominal aorta, cervical artery dissection and dissected aneurysm of the renal artery were noted. One patient showed aneurysms of the renal artery and the splenic artery. Two patients were presented with CCFs, those were occluded with detachable balloons. Three patients showed a history of spontaneous hematoma. One patient (11–yr-old boy) was presented with spontaneous bowel rupture and congenital cystic adenomatoid malformation of the lung. Six patients showed easy bruising and 5 patients revealed thin transparent skin with visible veins. One hospital death occurred from uncontrolled bleeding after acute type B aortic dissection. Genetic analysis showed missense mutations in 5 patients and a duplication of 15 base pairs in 1 patient. In one patient, no mutation was observed in COL3A1. Conclusion: Because EDS IV is a life-threatening vascular disease with very high surgical morbidity and mortality. For recognition of this disease, high degree of suspicion is mandatory and genetic testing of COL3A1 should be performed in suspected cases.