The combination of radiotherapy and surgery plays a major role in treating pelvic cancer. However, this technique is chiefly limited by the radiosensitivity of the small bowel following postoperative radiotherapy. In this situation the small bowel is not protected because of its lack of mobility. A radioprotective prosthesis is presented which is readily removable and whose purpose is to push the small bowel out of the pelvis during radiotherapy, thus protecting it from radiotherapy. If required, a simple system allows the prosthesis to be emptied and refilled between courses of radiotherapy, if required, without reoperation. This technique has been used in 4 patients: 2 had rectal carcinoma secondary to ulcerative colitis in one case and to Crohn's disease in the other; the other 2 cases were recurrent rectal carcinoma, one of which was partially resectable. When radiotherapy was completed the prosthesis could be deflated and removed through a short incision under local anesthetic. In the medium term, no small bowel complications were observed in spite of high-dose radiotherapy. When used for radiosensitive pelvic tumors, this technique combines low cost and ease of use with very low morbidity and the possibility of administering high-dose radiotherapy.