The Mitrofanoff principle, first described in 1980, consists of implanting a tubular organ such as the appendix, ureter, or fallopian tube into the wall of the bladder (or urinary reservoir) to create a non-refluxing, catherizable urinary conduit. Between 1993-1996, 7 men and 1 woman (aged 48-64, average 59) underwent radical cystectomy and urethrectomy combined with the creation of a MAINZ I urinary reservoir (based on the Mitrofanoff principle). In men the indication for the procedure was the diagnosis of invasive transitional cell carcinoma of the bladder with involvement of the prostatic urethra. All patients had refused urinary diversion to an ileal conduit because of its deleterious effect on the quality of life. In all patients the postoperative course was uneventful, apart from intraperitoneal urinary leakage from the reservoir in 1, successfully managed conservatively. The patients have gained full control of urinary drainage, performing intermittent self-catheterizations every 4-5 hours. In 3 patients there were difficulties with catheterization due to stenosis of the conduit, usually at the skin level. None have suffered leakage from the reservoir, during the day, even when it was full. Our experience shows that creation of a continent urinary reservoir according to the MAINZ I technique is an excellent surgical solution for patients in whom the creation of an orthotopic reservoir is impractical. The use of the umbilicus as a stomal site preserves normal body image and thus does not interfere with quality of life as in those undergoing radical cystectomy.