Although it has been known for more than a decade that Marfan syndrome - a dominantly inherited connective tissue disorder characterized by tall stature, arachnodactyly, lens subluxation, and a high risk of aortic aneurysm and dissection - results from mutations in the FBN1 gene, which encodes fibrillin-1, the precise mechanism by which the pleiotropic phenotype is produced has been unclear. A report in this issue now proposes that loss of fibrillin-1 protein by any of several mechanisms and the subsequent effect on the pool of TGF-beta may be more relevant in the development of Marfan syndrome than mechanisms previously proposed in a dominant-negative disease model. The model proposed in this issue demonstrates several strategies for clinical intervention.