With the availability of modern imaging modalities such as magnetic resonance imaging (MRI), contrast-enhanced computed tomography (CT), and transesophageal echocardiography (TEE), diagnostic options in the evaluation of Marfan patients have been improved profoundly. The most recent diagnostic advances comprise noninvasive tissue characterization of the aortic wall, immunofluorescence studies or pulse chase analyses of skin and cultured dermal fibroblasts, and molecular analysis at the cDNA/DNA level of the fibrillin-1 gene. New diagnostic insights have eventually led to revised nosologic criteria for the diagnosis of Marfan syndrome. The diagnostic reliability as well as the advantage and limitation of these recent diagnostic strategies are discussed; moreover diagnostic concepts for patients with neonatal as well as classic Marfan syndrome are presented and discussed in the context of the clinical management during adolescence, gravidity as well as in the pre- and postoperative patient.