Ninety-three consecutive patients with transfusion-dependent gastrointestinal bleeding from vascular malformations (VMs) underwent systematic assessment in our gastrointestinal laser suite with extended upper gastrointestinal endoscopy and colonoscopy. Of these patients, 83 had angiodysplasia and 10 had the Osler-Weber-Rendu (OWR) syndrome. The median age in each of these groups was 70 and 63 years, respectively. Cardiovascular disease, especially valvular disease, was common. A poor correlation existed between the results of endoscopically identified VMs and visceral angiography in patients with angiodysplasia. A combination of upper and lower gastrointestinal VMs was found in 11% of patients with angiodysplasia and 60% of those with the OWR syndrome. All identified VMs were completely obliterated by photocoagulation with use of a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser. Bleeding was successfully controlled in 9 patients with the OWR syndrome and in 72 patients with angiodysplasia (range of follow-up, 1 to 39 months). In 243 laser treatments, 3 perforations and 5 episodes of delayed bleeding occurred. This experience demonstrates that extended upper endoscopy is useful in identifying VMs and that gastrointestinal bleeding from VMs can be safely and successfully controlled with use of endoscopic Nd:YAG laser therapy.