A 3-year-old boy with early rupture of an aortic aneurysm due to infantile Marfan's syndrome is presented. In an emergency operation we prepared a composite graft using a 17-mm St. Jude prosthesis with an 18-mm vascular conduit. The postoperative period was complicated by pneumothoraces, transient bilateral phrenic nerve paralysis, cerebral convulsion, and supraventricular tachycardia. Four months postop the composite graft was replaced with an aortic homograft due to severe stenosis. His condition after 12 months is excellent.