Small intestine injury causes long-term suffering and high mortality. Five of 187of our patients had developed serious small intestine injury. Four patients had corrective surgery. Three patients died. All were women. Subsequently, all patients who received definitive pelvic irradiation had small intestine roentgenograms to determine itslocation and mobility. Female patients, thin patients, and elderly patients had larger amounts of small intestine in the whole pelvis, a deeper cul de sac, and a greater incidence of relatively immobile small intestine. Patients with relativelyimmobile small intestine in the treatment field may be predisposed to injury. There wasno relationship of the incidence of relatively immobile small intestine to prior pelvicsurgery. We used the findings from the small intestine roentgenograms to modify indiviually the radiotherapy regimen so as to minimize the risk for small intestine injury. Patients were placed in the prone position to displace the small intestineout of the treatment fields used for booster dose irradiation. The treatment field wasmodified to exclude the small intestine. The total tumor dose delivered was determinedby expectations for curve vs. complications. To date, none of the patients in this study group has developed small intestine injury. Cadaver studies showed the feasibility of elective shortening of the pelvic cul de sac. The small intestine can be displacedaway from the bladder, prostate, or cervix.