The occurrence of a fistula between the duodenum and the colon is very rare, although these two structures commonly lie in intimate relationship to each other. It is not uncommon for tumor of the right colon and proximal transverse colon to involve the duodenum by continuity, but fistulous connection between the duodenum and colon are infrequent In most of the reported malignant cases, the fistulas follow carcinomas of the transverse colon or the hepatic flexure of the colon. We report a rare case of malignant duodenocolic fistula which was first suspected by endoscopic examination and confirmed by operation.