Bleeding ectatic vascular lesion involving the sigmoid colon, endoscopically indistinguishable from angiodysplasia, in an 8-yr-old boy. An 8-yr-old Japanese boy was hospitalized, complaining of active hematochezia. He was shown to have a cherry-red, blood-oozing area of vascular dilation with mucosal prominence in the sigmoid colon by endoscopy, but had no other mucocutaneous vascular abnormalities. A family history was noncontributory. Under the clinical diagnosis of angiodysplasia of the sigmoid colon, he underwent an elliptical resection of the part, based on the intraoperative endoscopic findings. However, histological examination of the surgical specimen revealed a totally different picture from that seen in angiodysplasia: the thin-walled, markedly ectatic, nontortuous veins with hemorrhage were seen only just below the muscularis mucosae, around which the normal ones were shown to coexist. He has had no rebleeding for the past 3 yr. This lesion is considered to be an isolated congenital visceral telangiectasia involving veins. 