Arterioenteric fistula is rare but can cause life-threatening bleeding. A case of Crohn's disease with severe gastrointestinal hemorrhage caused by iliac arterioenteric fistula is presented. A 36-year-old male with Crohn's disease was admitted because of massive lower gastrointestinal bleeding, which required transfusion of 16 units of packed RBCs over 2 days. Radioisotope RBC scan revealed intestinal bleeding directly from the right iliac artery. Emergent operation confirmed iliac arterioenteric fistulae with active bleeding, There was no further intestinal bleeding after surgery. Remission had been maintained for 3 years with mesalazine.