Adenocarcinomas arising at ileostomy sites in patients after colon resection for various diseases, such as ulcerative colitis (UC), familial adenomatous polyposis coli, and Crohn's disease, are rare occurrences but have been reported increasingly in the last 20 years. We report a case of adenocarcinoma arising in an ileostomy site in an 85-year-old woman with longstanding UC. She had pancolitis and underwent total proctocolectomy. Thirty-nine years later, her ileostomy site developed a granulation tissue-type lesion, which on initial biopsy revealed cytologic atypia in the presence of marked inflammation. A subsequent biopsy revealed adenocarcinoma with signet-ring cells and abundant extracellular mucin. Resection of the ileostomy was undertaken and a new ileostomy was performed. The literature on adenocarcinoma arising in the 23 patients with ulcerative colitis who received a Brooke or Kock ileostomy and had no prior history of neoplasm is reviewed.