Wall dissection is a typical complication in the evolution of Marfan aortic aneurysm and usually is associated with valve regurgitation. Formation of a fistula with adjacent structures is very uncommon. We report the case of a 32-year-old man who presented with the typical features of Marfan's syndrome, with chronic aneurysm of the ascending aorta and acute aortopulmonary fistula. Diagnosis was made preoperatively by aortography; operation was performed successfully. A review of the literature only shows a few cases of aortopulmonary fistula in atherosclerotic, syphilitic, or postendocarditis disease.