All giant-cell tumors were considered at one time to be malignant lesions and were classified by the term "giant-cell sarcoma." As knowledge concerning their true nature increased, it became evident that some of them were benign lesions and curable by means of surgical removal. I believe that the term "giant-cell sarcoma," when used in reference to benign giant-cell tumor, has been partly responsible for the confusion that has existed in the classification and study of this particular group of bone lesions. In a previous publication I1suggested the use of the terms "benign giant-cell tumor" and "malignant giant-cell sarcoma" in an attempt to clarify the differentiation. Although surgical treatment resulted in many cures of patients who had these tumors, I became wary in my prognosis for I found that occasionally there was recurrence of the lesion, and in some instances metastasis occurred. Some physicians concluded that meddlesome surgical intervention