This is a case report of a patient presenting with rectal carcinoma and Crohn's disease. Adjuvant treatment was considered to be mandatory on the basis of local extension. Therefore a Silastic Tissue Expander Prosthesis (STEP), connected with a subcutaneously located self-sealing valve system, was introduced surgically to push small bowel up out of the treatment portals. Patient received 55 Gy without any acute or late complication. This easy technique allows radiotherapy in conditions where complete elimination of small bowel outside the treatment volume is required.