Tuberculosis is common disease in developing countries manifested by multi-organ involvement. Although the incidence of tuberculosis has been reducing recently due to the advancement of anti-tuberculosis chemotherapy, improvement of public health, and early diagnosis, the rate is still higher in developing countries. The diagnasis of colonic tubcrculosis is difficult due to its frequency, vague manifestation, and difficulty in confirming the disease process. Fortunately, the advent of flexible colonoscopy has provided an opportunity to confirm the diagnosis of colonic tuberculosis, however biopsy can frequently leveal false negative results. A-27-year-old man was admitted with a 2 week history of rectal bleeding. He complained of anorexia, abdominal pain, and weight loss. Routine laboratory tests and chest X-ray findings were within normal limits, with the exception of left pleural thickening. A colonoscopy showed irregular and small, multiple, and shallow polypoid mucosal lesions in the ascending colon and multiple ulcers in the transverse colon. Multiple colonic biopsies suggested tuberculosis. After three months of prirnary anti-tuberculosis medica tion, the patient showed slightly improved coiono- scopic findings. Follow-up colono- scopic findings revealed more aggrevation and chest X-ray findings showed multiple patch consolidation in the left lung field. Primary anti-tuberculosis medication was stopped and substituted for secondary anti-tuberculosis medication. When clinical and colonoscopic methods are found to be compatible with intestinal tuberculosis in countries with a high prevalence of colonic tuberculosis, a therapeutic trial with an antituberculosis agent is usually considered. In a failed therapeutic trial, considerations must be made not only to other inflammatory bowel diseases such as crohn's disease, but also to multi-drug resistance tuberculosis. (Korean J Gastrointest Endosc 18: 591-596, 1998)