Eight patients with anal blood loss were referred for endoscopic polyp removal (4) or because of problems with the differential diagnosis (4). These patients were referred because of an apparent discrepancy between the initial diagnosis (malignancy, ulcerative colitis and hemangioma) and the clinical and/or radiographic and endoscopic findings. At endoscopy a polyp-simulating lesion was found in all patients; this was not adenomatous in nature, but was made up of bright red, hyperemic prolapsing redundant mucosa. Also, polypoid excrescences were present with a clearly distinguishable transition between the intensely red congested mucosa and the normal pink adjacent epithelium at the base of the stalk. The distribution of the lesions was confined to the sigmoid area. After institution of a fibre-enriched diet, regression of the lesions was documented. However, the conspicuous hypercontractility and thickening of the mucosal layer persisted. The clinical significance of the recognition of this polyp-simulating mucosal prolapse syndrome lies in the fact that endoscopic polyp removal is not indicated and that such abnormalities may be responsible for low-grade, chronic and recurrent bleeding.