Our aim was to report our experience with treating GI bleeding in patients with hereditary hemorrhagic telangiectasia (HHT).Consecutive patients with GI bleeding referred to the Yale University Vascular Malformation Center underwent clinical evaluation and endoscopy. Hb and blood transfusion requirements for 1 yr before and after evaluation were documented. Patients with a mean Hb or= 12 units packed red blood cells (PRBC)/yr were defined as patients with significant bleeding. Drug therapies, including ethinyl estradiol/norethindrone, danazol, and aminocaproic acid, were prescribed on an individual patient basis.The study included 43 HHT patients with a mean age of 57 yr. Endoscopy revealed telangiectases in the esophagus (1/41), stomach (33/41), duodenum (33/41), jejunum (5/9), and colon (10/32). Patients with > 20 telangiectases visualized on esophagogastroduodenoscopy had a significantly lower mean Hb of 7.9, compared with 9.4 (p = 0.007), and a trend toward higher blood transfusion requirements. Non-HHT-related causes of GI bleeding were diagnosed in four patients. During a mean follow up of 18.9 months, the group of 40 patients with HHT-related bleeding had improvements in their mean Hb and blood transfusion requirements.Some HHT patients with GI bleeding improve on drug therapies, but others fail. Transfusion-dependent GI bleeding is difficult to manage, and optimal management may include both medical and endoscopic treatments.