Of 362 patients undergoing ileal pouch-anal anastomosis, 12 (five with chronic ulcerative colitis and seven with familial adenomatous polyposis) had 16 associated carcinomas. Incidental carcinoma was found in four patients who had undergone ileal pouch-anal anastomosis, six patients had known carcinoma, and carcinoma was suspected in two patients with high-grade dysplasia. No tumor was Stage C or D. After a median observation period of 24 months, no evidence of recurrence was documented. Data suggest that patients with carcinoma complicating chronic ulcerative colitis and familial adenomatous polyposis can safely undergo ileal pouch-anal anastomosis; however, it may be prudent to perform resection and later ileal pouch-anal anastomosis after a period of observation and appropriate adjuvant therapy because of the difficulty in intraoperative staging.