Freezing is lethal for cells and may be used to destroy normal or neoplastic tissue.1,2Our experience with cryotherapy for malignant tumors in the oral cavity demonstrated that lesions which were radioresistant and were not amenable to excision could be controlled.3When the cancer was adjacent to the mandible or maxilla, the bone also was frozen during treatment and was exposed when the soft tissue sloughed a few days later. Although the bared bone became discolored and coated with necrotic debris, healing occurred and soft tissue slowly covered the area. These observations suggested an experimental study to determine the extent of cell destruction and the manner of subsequent regrowth in bone devitalized by freezing without having been removed from the body. The purpose of the experiments was the development and evaluation of a technique of treating bone tumors without amputation or excision. Methods and Materials The femora of