THE radiation therapy of bone tumor has not been prosecuted with any degree of enthusiasm, and statistical reports are so unconvincing that no one is justified in drawing conclusions from the scanty literature on the subject. The direct question confronts us: Has radiation therapy of bone tumor proven of sufficient value to be seriously considered as a promising therapeutic agent in this field of pathology? It may be asserted that radiation has at least accomplished as much in bone tumor as any other type of treatment heretofore considered and used, but such a claim would not be sufficient to stimulate further study in this direction. From personal experience, we feel that we can look upon radiation as holding out a distinct promise, though we are not as yet on thoroughly proven ground. The bone field for radiation therapy is sharply denned. Simple bone tumors, including exostoses, certain types of bone cysts and chondromas, are distinctly surgical problems. On the other hand, inflammatory tumors, sarcomas and carcinomas, are, in our opinion, preferably to be considered radiological problems. One year ago, one of us (W. E. C.) presented a report before this Society wherein three apparently clinical cures could be claimed in cases from our own service. These three cases have just been rechecked and found to be normal at this date. Since then, we have added another even more striking case that we had lost track of, but upon which complete data will be presented herewith. A brief résumé of this fourth case is as follows: Mrs. S. K., age 56, adamantinoma right lower jaw. Reported for treatment February 13, 1922. Patient first noticed some enlargement of the right jaw and cheek about twenty years ago, a condition which increased gradually. The growth interfered with eating and, about eight years ago, she consulted a physician. At that time some teeth were pulled, but her physician advised her that it would be unwise to attempt operation. After this, she consulted several other surgeons and was advised that nothing could be done. The X-ray diagnosis was adamantinoma. During the past year the tumor had been enlarging more rapidly than before. General health good. No pain, but considerable difficulty in eating on account of poor dental occlusion. Wassermann negative. Examination.—Marked swelling of right lower jaw and cheek by a rounded mass about 8 to 10 cm. thick in its widest diameter. Tissue is of stony hardness. Protrusion of mass into floor of mouth, with misplacement of gum and teeth. Treatment commenced March 31, 1922. Radium needles were buried into the mass from the inside of the mouth and heavily filtered high voltage X-ray was applied externally. The X-ray treatment was repeated several times during the following two years. Nearly two years have elapsed since the patient received the last X-ray treatment. The skin looks normal—tumor mass can scarcely be made out from inspection. Some enlargement still remains in lower ramus.