We report a case of carcinosarcoma in the transverse colon in a 60-year-old woman. She was admitted to our hospital for further examination of occult blood in October, 1995. Colonoscopy disclosed an elevated lesion with ulceration in the transverse colon, and she underwent right hemicolectomy. Histopathological examination revealed the tumor to consist of both carcinomatous and sarcomatous elements, the latter being more predominant. Immunohistochemistry revealed vimentin immunoreactivity in most of the sarcomatous cells, and S-100 and myoglobin in a few carcinomatous cells. Distinct carcinomatous features were noted in one superficial portion of the tumor, and these carcinomatous cells showed immunoreactivity for epithelial membrane antigen. The patient is alive 14 months after surgery without evidence of recurrence. To our knowledge, this is the fourth reported case of carcinosarcoma of the colon. Our review of the literature disclosed poor prognosis in colonic carcinosarcoma.