The life expectancy of patients with the Marfan syndrome is reduced by complications caused by dilatation of the ascending aorta. Because surgical therapy with a composite graft may alter this natural history, we analyzed the preoperative and long-term postoperative status of 50 consecutive patients who received such a graft. At surgery, the patients had a mean age of 32.2 years and a mean aortic diameter of 7.1 cm (range, 5.3 to 10). Dissection of the ascending aorta was present in 14 patients and was acute in 5. None of the 44 patients who underwent elective repair, and only one of the six patients who had emergency surgery, died in the hospital; thus, the overall hospital mortality was 2 percent. Five of the 49 survivors died during a follow-up period of up to eight years (10.2 percent late mortality). During the most recent four years of evaluation of this series (38 patients), no postoperative deaths due to intrathoracic problems occurred. Actuarial survival was 87 percent at both two and five years. Composite-graft repair of the ascending aorta in patients with the Marfan syndrome can be performed with low operative and long-term mortality. Because of the unfavorable natural history of the Marfan syndrome and the potential for dissection in moderately dilated aortic roots, we recommend prophylactic repair when the aneurysm reaches a diameter of 6 cm.