Marfan syndrome is a genetic disorder of the connective tissue caused by mutations in FBN1 gene. There are approximately 2-3,000 Marfan patients in The Netherlands. It has a broad clinical spectrum with features in most organ systems. Aortic root aneurysm is the most important clinical problem in these patients as it is progressive and leads to dissection and rupture if untreated. Endocarditis prophylaxis is indicated in all Marfan patients with aortic root aneurysm and operated patients. Timely diagnosis and specialized patient care are essential for the prognosis of this disease.