An experimental study on dogs was conducted to evaluate if urine immersion contributes to the stenosis of the reimplanted ureter. Four female dogs were used. One ureter was left untreated as control. Two ureters were reimplanted by Leadbetter-Politano technique and five ureters were reimplanted by Le Duc technique. The dogs were evaluated in the 4th postoperative month. The follow-up studies included urine analysis, serum creatinine, intravenous urography (IVU), cysto-gram and histological study. Two reimplanted ureters (40%) showed mild stasis of contrast me-dium by Le Duc technique in IVU. Histology showed inflammation and fibrosis of ureteric adven-titia over the exposed side and retardation of overlying mucosal regrowth in two ureters by Le Duc technique. On the contrary, the untreated ureter and two ureters reimplanted by Leadbet-ter-Politano technique were grossly and microscopically normal. Our preliminary results showed that urine immersion of the reimplanted ureters may contribute to inflammation and fibrosis of ureteric adventitia. However, more animal studies and long-term follow-up are needed to confirm the clinical significance of inflammation in making the stricture or reflux of the reimplanted ure-ters.