There is considerable interest in assessing patients with Marfan syndrome at the clinical, protein, and genetic levels. Clinical assessments are inconsistent between centres and between clinicians. There are no satisfactory clinical grading scales against which to analyse the molecular information, limiting the scope of clinical/ molecular correlations. We present grading scales for the major clinical systems involved in Marfan syndrome and suggest that their widespread use will facilitate collaborative approaches to clinical/ molecular correlations and international assessments of therapy.