Anatomo-radiological study of a case of osteolysis of the femoral head and neck in a 56-year old male who had recieved, 22 years earlier, an intense radiotherapeutic treatment for a soft tissue tumour of the corresponding hip region. The treatment is considered as being the main etiological factor responsible for the bone lesions. The latter seems to have been favored by an indolent joint due to a thoracic cordotomy for post-irradiation pains; it may have been prepared by a secondary osteodystrophy which preceded the radiotherapy and seems due to two previous surgical excisions.