The rate of tuberculosis has been significantly decreased due to development of effective antituberculosis chemotherapy. Tuberculosis of the duodenum is very rare and diagnosis is very difficult because of nonspecific symptoms and nonspecific duodenal lesions. A case of duodenal tuberculosis which was clinically diagnosed as malignancy of the duodenum was discovered. The diagnosis was confirmed by a subsequent operation and administration of antituberculous chemotherapy resulted in a positive response. Consequently, the following is a report on this case, review of related literature. (Korean J Gastrointest Endosc 18: 257-261, 1998)