Colonic varix, which is a rare cause of lower gastrointestinal bleeding, can be developed by various diseases. Colonic variceal bleeding is more fatal than esophageal variceal bleeding. Klippel-Trenaunay-Weber syndrome is a rare congenital vascular malformation characterized by the clinical triad of bony or soft tissue hypertrophy, hemangioma and varicosities or vascular malformations. We report a 42-year-old female patient with fatal sigmoid variceal bleeding. She had dilated vessels over her body and face, and both superior and inferior vena cava were obstructed. She underwent an emergent operation due to uncontrolled massive bleeding from sigmoid varices. We report a case of Klippel-Trenaunay-Weber syndrome with literature review. (Korean J Gastrointest Endosc 2003;27:2125)