A retrospective analysis was performed to determine the surgical outcome and long-term follow-up of patients with documented cystic medial necrosis of the aorta. Ninety-three patients were diagnosed as having cystic medial necrosis at the Cleveland Clinic between July 1963 and December 1987 (72% men aged 26 to 77 years, mean 55). Patients who met the standard diagnostic criteria for Marfan's syndrome were deliberately excluded. Sixty-eight percent of the patients had a diastolic murmur and chest roentgenogram revealed a dilated aortic arch in 58% and cardiomegaly in 63%. Cardiac catheterization in 76 patients demonstrated aortic root dilation in 78%, aortic regurgitation in 72%, aortic dissection in 32% and coronary artery disease in 32%. Ninety patients underwent surgery including composite graft repair with reimplantation of the coronary arteries in 34%. Follow-up, obtained on 90 (97%) of the 93 patients, ranged in duration from 0 to 137 months (mean 29). Thirty-four of the 90 patients died (age range 30 to 75 years, mean 60). Ninety-four percent of the known causes of death were related to the cardiovascular system; 65% were the result of aortic dissection or rupture or sudden death. Ninety-six percent of survivors were in New York Heart Association functional class I or II. Overall estimated survival at 1, 3 and 5 years was 72.2%, 63.5% and 57.4%, respectively. Actuarial survival in patients who underwent composite graft reconstruction was 84% at 5 years. The presence of a diastolic murmur at initial presentation was associated with a poor prognosis (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)