Recurrent severe hemorrhage from intestinal vascular malformations, although extremely rare, may be associated with significant morbidity and mortality. The treatment may require extensive surgical resection, vascular embolization, and repeated blood transfusions. An adolescent boy with the Klippel-Trenaunay syndrome involving the pelvis and left leg presented with recurrent life-threatening hematochezia associated with defecation. Endoscopy documented that the bleeding originated from the submucosal venous angiomata in the region of the hemorrhoidal plexus. An argon laser was used to systematically coagulate the venous angiomata involving the distal 7 cm of the anorectal canal. Postoperative minor rectal bleeding and rectal tenesmus resolved in a few days. The patient has had only one brief episode of hematochezia in more than 4 years of follow-up. The use of the argon laser has provided effective palliation of colorectal vascular malformations with minimal morbidity but more importantly has allowed the preservation of normal anorectal function.