A 53-year-old male presenting with a 3-month history of intermittent mild rectal bleeding was found, on double contrast barium enema, to have a large polyp on a long stalk in the sigmoid colon. Large bowel endoscopy confirmed the presence of a 2 cm pedunculated polyp which was removed using a diathermic snare, with slight bleeding following the procedure that did not require endoscopic haemostasis. Only after histologic examination was the polyp shown to be a colonic arteriovenous malformation. Endoscopically, arteriovenous malformations generally appear as flat or elevated bright red lesions. A pedunculated polypoid appearance is extremely uncommon. In this case, no gastrointestinal bleeding or polypoid recurrence was observed during the 12 months of clinical and endoscopic follow-up.