Fibrous dysplasia of bone is a relatively rare condition characterized by fibrous tissue replacement of skeleton, usually not disabling, of slow progress, and showing a tendency to become arrested. It may be monostotic (confined to one bone) or Polyostotic (situated in many bones). The etiology of fibrous dysplasia is unkown but it is now believed to be a developmental error in which primitive fibrous tissue proliferates within the bony medulla and encroaches upon the cortex from within. This paper reports the one case of polyostotic fibrous dysplasia. The diagnosis was made by clinical, radiological and histological findings. The review of literatures was made briefly.