An interest fistula is a life-threatening complication when associated with the treatment of pelvic cancer. Such fistulae arise in 10% of patients treated by the combination of aggressive surgery and radiation therapy. Nineteen such occurrences developing in 245 patients who had pelvic exenterations are used to demonstrate the need for directing immediate attention toward correcting the physiologic and metabolic abnormalities created by the fistulae. Local control of the fistulae is facilitated by techniques for identifying its cause and precise location.