Fistulous communications between the intestinal tract and the urinary bladder are not rare, and the diagnosis is usually simply made. However, in a recent case seen in this clinic, this lesion was so dramatically demonstrated during the course of administration of a barium enema that the incident is considered unusual enough to form the basis of a case report. The patient was a 65-year-old woman, who was referred to the X-Ray Department with a dia gnosis of “diverticulitis and stricture in the sigmoid region.” No other information was supplied. At the beginning of the examination the rectal ampulla ballooned out well and there was then some delay at the rectosigmoid junction. At this time barium began to escape around the rectal nozzle but, as no signs of discomfort appeared, th e examination was continu ed. In rotating the pati ent to examine the recto sigmoid region more thoroughly, a large, smoothly margined, barium-filled viscus was seen anteriorly and was thought to represent a redundant sigmoid. When the patient was returned to the supine position, a streak of contrast medium was observed moving from the pelvic region up toward the head. At first this was believed to be barium on the table top, since the enema was coming out as fast as it was going in. It soon became apparent that it really was barium flowing up the right ureter, since the right kidney pelvis became filled. The flow of barium from the can was immediately stopped, but by this time the left ureter was filled and the left renal pelvis partially so. Films were made quickly, and the enema can was lowered to the floor to allow as much of the contrast medium as possible to run out. The rectum and what apparently was the urinary bladder were almost completely emptied before th e patient left the examining table. Another film was made approximately four hours after the original examination. The kidney pelves were clear , as were both ureters except for a small residuum of barium in the terminal portion of the one on the right. In checking the patient's clinical chart, it was found th at some years previously she had had a perforated sigmoid diverticulum, following which there had been all the signs of a rectovaginal fistulapassage of gas and feces by th e vagina, etc. More recently she had been passing some feces and gas when urinating. A proctoscopic examination had been attempted but, because of scar tissue in the rectosigmoid, was not satisfactory. There were no ill effects from the experience and the patient's kidney function did not seem to be impaired in the least , as was shown by a normal intravenous pyelogram the following day. A colostomy was later performed, preparatory to a repair of the fistula, and the patient was doing well at the last report. The unusualness of this situation, which, as far as we could determine, is rarely encountered, prompted us to prepare and submit this case report.