About 30 cases of fibrous dysplasia associated with one or more myxomas (Mazabraud's syndrome) have been reported since 1926. We report a new case in a woman with polyostotic fibrous dysplasia and a myxoma in the left femoral muscle. She also had a history of precocious sexual development and café au lait spots, two manifestations whose association with polyostotic fibrous dysplasia defines McCune-Albright syndrome.