During the period from Jan. 1, 1942, to Oct. 1, 1945, 656 patients were admitted to an army hospital designated as a radiation therapy center. Of this number, 25 had primary bone tumors, including 10 giant-cell tumors in the diagnosis or treatment of which we participated. A number of other giant-cell tumors were seen in consultation with other installations or as follow-up cases. Our opinions are influenced, also, by our experience prior to active military service and to some extent by the views of others as expressed in various publications. No statistical study will be attempted; cases presented are illustrative of certain features of the disease. In this hospital all cases were seen by a tumor board composed of a radiologist, pathologist, surgeon, and internist, and by representatives of appropriate specialties in selected cases. The decision as to the method of treatment was made by this board. Those desiring a review of the historical aspects of giant-cell tumors are referred to the bibliography. Important data are contained in the articles by Kolodny (20), Kirklin and Moore (19), Geschickter and Copeland (13, 14), Leucutia, Witwer, and Belanger (21), Pfahler and Parry (26), and Jaffe, Lichtenstein, and Portis (16). Methods of Treatment While most giant-cell tumors are benign, there is evidence to indicate that some are malignant from the outset or eventually become malignant. When tumors thought to be benign are later proved to be malignant, it would seem more reasonable to assume a lack of diagnostic acumen in the first place than to attribute malignant change to curettage, roentgen therapy, or infection. We believe that each case should be studied clinically, roentgenographically and, where possible, by biopsy. Malignant cases should be treated by radical surgical methods where the lesion is accessible. Cases that appear to be benign should be treated conservatively. Both roentgen therapy and conservative surgical methods give good results. Surgical methods, however, cannot be successfully used when the lesion is inaccessible, as in the spine or pelvis. Our personal preference is for roentgen therapy in all benign giant-cell tumors. It has been pointed out in the past that following a series of x-ray treatments some giant-cell tumors temporarily increase in size and show an aggravation of symptoms. A period of many months is required before the final results of radiation therapy are obtained. Our experience has been that this temporary increase in the size of the tumor, with aggravation of symptoms, does occur in some cases. Instances are encountered in the literature where surgery has been resorted to within two months following roentgen therapy and the statement is made that irradiation was unsuccessful (15). Such a conclusion is not justified.