Abstract
1. Four cases of periosteal ganglion are described. Their relationship to other mucin-filled cysts of connective tissue, both in soft tissues and in bone, is discussed and the fact that they all result from mucoid degeneration of fibrous tissue is emphasised.
2. Treatment is by surgical excision, with removal of a margin of apparently normal periosteum as well as the lesion itself. The lesion may recur, even after apparently adequate excision, by mucoid degeneration taking place in the periosteum immediately adjacent to the operative site or in the connective tissues occupying the surgical defect.