Eight patients who had polyostotic fibrous dysplasia were followed up for more than 10 years. One had the Albright syndrome. Two of 3 proximal femoral lesions which were treated before puberty by either curettage and bone grafting or by osteotomy, developed progressive deformity during the growth period. One of 2 proximal femoral lesions treated by curettage and bone grafting after the age of 18 also developed a deformity. Two tibial lesions operated on at the age of one and 30 years remained stable. The histological findings showed more active lesions in young patients compared with adults.