Several recent articles (3–7) have again called attention to the importance of radiation effects upon growing and adult bone. Whereas it was formerly thought that adult bone is one of the most radioresistant of normal tissues, it is now recognized that it is the soft-tissue components of the bone, such as the terminal blood vessels of the haversian and Volkmann's canals, which may be particularly affected by hyperemia and later by obliterative endarteritis. Another reason for the interest in this subject is the present tendency toward the use of higher and higher voltages for therapy, with delivery of increasing amounts of radiation to the deeper tissues. In spite of the fact that there is less differential absorption by bone from these higher voltages, nevertheless fractures have occurred following such irradiation just as with conventional cross-fire therapy, regardless of whether or not lateral pelvic portals were used. It should be remembered that the blood supply to the femoral head and neck comes fr...