Thirteen patients with giant cell tumor of bone were treated with megavoltage irradiation during 1958-1972. Nine cases were believed to be true giant cell tumors of bone. The only patient with recurrence following a geographic miss was salvaged surgically. Curative therapy for giant cell tumor of bone may be 3500 rads in 15 fractions in 3 wk. It is well tolerated with minimal morbidity. Special care must be used in interpretation of the post-therapy radiologic appearance of these lesions because an initial period of osteolysis lasts many weeks before any radiographic indication of healing by recalcification occurs.