We reviewed the records of 28 patients with Marfan syndrome and 30 age-matched control patients with presumed isolated pectus excavatum to determine the outcome of surgical repair of the pectus deformity in Marfan syndrome. One third of the patients with Marfan syndrome underwent repair of the pectus excavatum before diagnosis. Of the 30 patients with "isolated" pectus excavatum, 17 had findings by history or physical examination, such as mitral valve prolapse, scoliosis, or a relative with pectus excavatum, suggestive of an underlying disorder of connective tissue. Pectus excavatum of more than moderate severity recurred in 11 of 28 patients with Marfan syndrome and was associated with young age at initial surgery and lack of temporary internal stabilization of the chest after surgery. Only two of the control patients had recurrence of the defect; one of these patients had findings suggestive of an underlying heritable disorder of connective tissue. We conclude that pectus excavatum may indicate the presence of an underlying heritable disorder of connective tissue such as the Marfan syndrome. In patients with Marfan syndrome, and possibly other inherited connective tissue disorders, surgical repair should be delayed if possible until skeletal maturity is nearly complete and should employ internal stabilization.