Twenty cysts were treated by excision of most of the cyst wall, including bone, and grafting with struts of autologous or homologous bone. Eleven cysts were in the active phase and nine were in the latent. All but one was cured without recurrence, and that cyst healed after a second operation. The ages of the patients with active cysts ranged from four and a half to ten years; one patient was twelve years old. Data on twenty other patients, some treated by curettage and bone-grafting and some (six) in whom early healing followed fracture, are also given.