PURPOSE: The aim of the present study was to evaluate the biocompatibility of small intestine submucosa (SIS) in the reconstruction of the ureter in swine. MATERIALS AND METHODS: An experimental study was performed in 10 half-breed pigs weighing between 20 and 30 K, in which a previously prepared segment of SIS measuring approximately 2.0 cm was implanted in the upper third part of the right ureter. RESULTS: Of the 10 operated animals, one died 14 days after the surgery due to a dehiscence on the suture line of the implanted graft. The remaining 9 animals were submitted to ultrasound examination of the urinary tract and were sacrificed on the 40th postoperative day. The macroscopic evaluation showed no calculus, incrustation, fistula, abscesses or adhesions in the ureters with the graft. Microscopic evaluation with hematoxylin-eosin and Sirius red showed in the experimental area (graft) the presence of urothelium in 100% of the cases, collagen in 100% of the cases, and smooth muscle layer in 87.5% of the animals. In the area adjacent to the graft (proximal and distal), we observed 92.86% of urothelium, 42.86% of collagen and 71.43% of smooth muscle. In the contralateral ureter, it was found 100% of urothelium and smooth muscle and just 11.11% of collagen. The microscopic analysis of the kidneys whose ureters received the graft of SIS evidenced congestion in 55.55%, pelvic edema in 66.66% and interstitial nephritis in 77.78%. Hydronephrosis was present in 33.33% and chronic pyelonephritis in 44%. Only 1 animal presented total absence of glomerulus in the renal parenchyma. CONCLUSION: The SIS graft behaved as a biological tissue support, allowing the regeneration of the urothelium and smooth muscle grow, despite of chronic inflammatory process.