SummaryThe clinical and roentgenologic findings typical of annular carcinoma of the colon are well known, and the diagnosis of this lesion is usually straightforward. However, when there is perforation of the neoplasm through the intestinal wall with the development of secondary inflammatory changes, both the clinical and roentgenologic features may be altered, and the correct diagnosis becomes more difficult to determine preoperatively. Some clinical and roentgenologic aspects of this type of chronic perforating carcinoma of the colon are discussed, using five selected cases as examples.