"Pouchitis" is a term for nonspecific mucosal inflammation of the pouch after total proctocolectomy and ileal pouch-anal anastomosis for ulcerative colitis. Pouchitis is the most frequent complication of the pelvic pouch at the late stage. To improve the accuracy of the pouchitis diagnosis, sets of clinical symptoms and endoscopic findings (with or without histology of biopsy samples) have previously been evaluated. Endoscopic findings are central to the diagnosis, and a universal consensus of various endoscopic findings must be the initial step toward an objective diagnosis of pouchitis. Since a proper signpost for the endoscopic evaluation of pouchitis has been absent, we developed this pouchitis atlas to minimize the diagnostic variation inherent among individual endoscopists. We also propose new criteria for the diagnosis of pouchitis: the Japanese criteria for diagnosis of pouchitis. These criteria are based on clinical symptoms and endoscopic findings that are clearly categorized in the atlas, and exclude infectious enteritis, anastomotic insufficiency, pelvic infection, anal dysfunction, and Crohn's disease. Advantages of the new criteria include ease of bedside diagnosis, without the calculation of points required by the other criteria for pouchitis. This pouchitis atlas, together with our new criteria, should contribute to the establishment of a clear-cut diagnosis for pouchitis and promote better evaluation and treatment of this novel intestinal inflammation.