The authors report three cases of peritonitis due to perforation of an ileal loop diversion. Two cases occurred 21 and 26 days after surgery with a persistent lesion at the base of the graft. The third case, much more unusual, occurred 8 months after the operation due to a stress ulcer in the ileal loop. The three patients were successfully treated surgically but the ileal loop diversion could only be preserved in one case: the other patients underwent cutaneous ureterostomy. The authors distinguish between fistulae of intermediate and late onset after the operation. The first type of fistulae can be prevented by improvement of the surgical technique and drainage. The second type of fistulae may develop whenever an associated arterial pathology is present.