We report and analyze two cases of Ehlers-Danlos syndrome (EDS) type 4. The first manifestation of the disease was a spontaneous perforation of the colon in a 47-year-old man; he was successfully reoperated on five years later for the rupture of an abdominal aortic aneurysm. Abdominal pain demonstrated the syndrome in a 33-year-old woman in whom multiple abdominal aneurysms were found. A ligation of the anterior tibial artery for spontaneous rupture was performed five years later. Light and electron microscopic studies of the skin disclosed similar alterations in both cases. The diameter of the collagen fiber bundles was reduced and the diameter of collagen fibrils was increased. It appears that EDS type 4 might be less characteristic than has been previously described. Classification of the different types of EDS according to electron microscopy is not possible.