PURPOSE: To evaluate the usefulness of CT in patients with gastrointestinal fistula. MATERIALS AND METHODS: We retrospectively reviewed the CT scans of 17 patients with various type of gastrointestinal fistula. The presence of these fistulae was confirmed by laparotomy in seven patients and by barium studies in fifteen. We evaluated the diagnostic accuracy of CT in these cases, and in correlation with barium studies and surgical findings, subsequently analyzed the CT findings. We determined the presence or absence of fistula tract, flow diversion of oral contrast media, bowel wall changes adjacent to the fistula tract, and extraluminal manifestations such as soft tissue mass, free air, leakage of oral contrast media, and peritoneal changes. RESULTS: The diagnosis of gastrointestinal fistula was possible on CT in nine (53%) of the 17 patients by using the CT criteria of direct visualization of the fistula tract (n=6) or flow diversion of oral contrast media (n=4). Other ancillary findings included bowel wall thickening adjacent to fistula tract in 15 patients, extraluminal soft-tissue mass in five, extraluminal free air in ten, extraluminal contrast leakage in four, and varying degrees of mesenteric and/or omental infiltration in 15. CONCLUSION: CT scanning is useful for the diagnosis of gastrointestinal fistula, which may be possible if the fistula tract and flow diversion of oral contrast materials are seen. It is also useful for evaluation of the extent of the etiologic disease.