Background and study aims: The purpose of this study was to evaluate dark-lumen magnetic resonance (MR) colono-graphy prospectively in patients with incomplete conventional colonoscopy. Patients and methods: Thirty-two patients with incomplete conventional colonoscopy underwent sameday dark-lumen MR colonography on the basis of a standard protocol. The depiction of colorectal diseases was assessed in the following colon segments: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The reasons for incomplete colonoscopy included high-grade stenosis in 26 patients (four with occlusive cancer, 12 with fibrotic stenosis based on recurrent sigmoid diverticulitis, eight with Crohn’ s-induced stenosis, and two with nonsteroidal anti-inflammatory drug colonopathy), extreme patient intolerance in one patient, and technical challenges associated with an elongated colon in five patients. The results of MR colonography were compared with the findings of the initial conventional colonoscopy, the histopathological outcome, and follow-up colonoscopy when possible. Results: All high-grade stenoses were confirmed on MR colonographic data sets. Of the 26 patients with high-grade stenosis, 19 underwent surgery with histopathological confirmation of the initial diagnosis. Follow-up colonoscopy was carried out in 14 patients with surgically treated high-grade stenosis. In six of these 14 patients, nine polyps identified at the initial MR colonography were confirmed and removed during a postoperative conventional colonoscopy. Two polyps (5 mm and 8 mm in diameter) identified on postoperative conventional colonoscopy had not been seen preoperatively at MR colonography. One polyp seen on MR colonography was not identified in the follow-up colonoscopy. Conclusion: Dark-lumen MR colonography is a feasible and useful method of evaluating the entire colon in patients with incomplete conventional colonoscopy. Background and research aims: The purpose of this study was to evaluate dark-lumen magnetic resonance (MR) colono-graphy prospectively in patients with incomplete conventional colonoscopy. Patients and methods: Thirty-two patients with incomplete conventional colonoscopy underwent sameday dark-lumen MR colonography on the basis of a standard protocol. The depiction of colorectal diseases was assessed in the following colon segments: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The reasons for incomplete colonoscopy included high-grade stenosis in 26 patients (four with occlusive cancer, 12 with fibrotic stenosis based on recurrent sigmoid diverticulitis, eight with Crohn’s-induced stenosis, and two with nonsteroidal anti-inflammatory drug colonopathy), extreme patient intolerance in one patient, and technical challenges associated with an elongated colon in five patients. The results of MR colonography were compared with the findings of the ini Of the 26 patients with high-grade stenosis, 19 underwent surgery with histopathological confirmation of the initial Follow-up colonoscopy was carried out in 14 patients with surgically treated high-grade stenosis. In six of these 14 patients, nine polyps identified at the initial MR colonography were confirmed and removed during a postoperative conventional colonoscopy. Two polyps (5 mm and 8 mm in diameter) identified on postoperative conventional colonoscopy had not been seen preoperatively at MR colonography. One polyp seen on MR colonography was not identified in the follow-up colonoscopy. Conclusion: Dark-lumen MR colonography is a feasible and useful method of evaluating the entire colon in patients with incomplete conventional colonoscopy.