The purpose of this study was to assess the predictive value of colonofiberscopy in the diagnosis of intestinal tuberculosis. The records of more than 14,000 colonofiberscopic examinations performed at the National Taiwan University Hospital from 1971 to 1995 were studied retrospectively. Colonofiberscopic diagnosis of intestinal tuberculosis required at least one of the following: circumferential ulcers, a single transverse axis ulcer with uneven base and elevated or nodular margin surrounded by nodular and hyperemic mucosa, or pseudopolyps. Sixty cases were diagnosed as intestinal tuberculosis based on these criteria, 29 of which were confirmed by histologic or bacteriologic findings or on the basis of clinical response to antituberculosis therapy. The positive predictive value of colonofiberscopy for intestinal tuberculosis was thus 43.3% (95% confidence interval 31-57%). Secondary intestinal tuberculosis with pulmonary tuberculosis accounted for 84% of cases. The most commonly involved area of the gastrointestinal tract was the ileocecal region, followed by the ascending colon and ileum. Based on our findings, colonofiberscopic examination with histopathologic and bacteriologic study of biopsy specimens is a powerful tool for the diagnosis of intestinal tuberculosis.