Patients who require cystectomy are usually treated with an ileal conduit or intestinal neobladder for urinary control. In some of them, however, the bowel segment cannot be used because of previous abdominal surgery or radiation treatment. Bladder transplantation from cadavers may be beneficial to these patients, if possible. To obtain basic knowledge about bladder transplantation, we developed an animal model of whole bladder transplantation in rats. Male Lewis rats weighing 270-320 g were used as both donors and recipients. Of the 23 recipients, 12 (52.2%) survived 7 days or longer after surgery. At 1 week after transplantation, the bladder showed loss of transitional epithelium and remarkable cellular infiltration. In the bladder at 5 weeks after transplantation, the transitional epithelium regenerated markedly and submucosal cellular infiltration was much improved. Regeneration of some smooth muscle cells was also noted. At 6 months after transplantation, the nerve fibers were recognized in the bladder and the volume of the transplanted bladder was well preserved (1.0-1.3 ml).This article describes an animal model of whole bladder transplantation in the rat which we produced and the results of our study. Because a large number of pure-bred animals can easily be used, we believe our rat model is very useful for basic studies of bladder transplantation.