The results of treatment of sixty-five symptomatic lesions in forty-three patients who had fibrous dysplasia were reviewed. For fourteen (93 per cent) of the fifteen times that a lesion in the upper extremity was treated non-operatively, the result was satisfactory. These results were independent of the patient's age when first seen. In contrast, in the lower extremity, the results were highly dependent on the age of the patients at the time of the initial presentation of symptoms. In patients who were eighteen years old or older, eight (88 per cent) of the nine times that a lesion involving the lower extremity had closed treatment and both times that a lesion was treated with curettage and bone-grafting, the result was satisfactory. The results of these modalities of treatment in patients who were less than eighteen years old were discouraging. Twenty-eight (88 per cent) of the thirty-two times that closed treatment was used and twenty-five (81 per cent) of the thirty-one times that curettage and bone-grafting was used, the result was unsatisfactory. However, after eighteen (86 per cent) of the twenty-one times that a lesion in the lower extremity was treated by internal fixation in a patient who was less than eighteen years old, there was a satisfactory outcome. We concluded that closed treatment of a symptomatic lesion in the upper extremity generally provides satisfactory results. In patients who are less than eighteen years old, neither closed treatment nor curettage and bone-grafting is adequate treatment for a symptomatic lesion in the lower extremity. Internal fixation should be strongly considered in these young patients.