Proteus syndrome (PS) is a disorder of patchy or mosaic postnatal overgrowth of unknown etiology. The onset of overgrowth typically occurs in infancy and can involve any tissue of the body. Commonly involved tissues include connective tissue and bone, skin, central nervous system, the eye, but it apparently can affect any tissue. Diagnosing of PS is difficult and the diagnostic criteria are controversial. Our group advocates stringent diagnostic criteria to facilitate research and appropriate clinical care. The benefit of strict criteria is that they define a clinical group that is reasonably homogenous with respect to manifestations and prognosis. The overgrowth of PS is progressive and can be difficult to manage. The progressive overgrowth most commonly causes severe orthopaedic complications, but it can cause many other complications. One of the most common complications in patients with PS is deep venous thrombosis and pulmonary embolism, which can cause premature death. Effective management requires knowledge of the wide array of manifestations and complications of the disorder and a team approach that includes the geneticist, surgeons, and other specialists.