Two patients were treated emergently for impending ruptured thoracic aortic aneurysms caused by type IV Ehlers-Danlos syndrome. One patient had typical physical evidence of type IV Ehlers-Danlos syndrome. The other patient had a normal phenotype. Type IV Ehlers-Danlos syndrome was diagnosed by electrophoresis of the collagen extracted from the skin. The clinician must be aware of the variations in presentation of type IV Ehlers-Danlos syndrome.