Inflammatory and ischemic bowel disease commonly involve a longer segment than a maligant lesion. The characteristic findings of inflammatory bowel disease are mucosal nodular hypertrophy and luminal narrowing. It has recently been reported, however, that the features of mucinous adenocarcinoma are similar to those of inflammatory bowel disease with long segmental involvement. After a brief review of the literature, we describe two cases of mucinous adenocarcinoma of the ascending colon associated with inflammatory disease. Because of long segmental involvement of the ascending colon, mucosal nodular hypertrophy and luminal narrowing, one of these was thought to be multiple villous adenoma with colitis, but was confirmed as mucinous adnocarcinoma. The other case, thought to be tuberculous enterocolitis, was comfirmed as tuberculous enterocolitis associated with mucinous adenocarcinoma.