BACKGROUND Postoperative hemorrhage, particularly delayed hemorrhage after pancreaticoduodenectomy, is a serious complication and one of the most common causes of mortality after pancreaticoduodenectomy. STUDY DESIGN The medical records of 500 patients who underwent pancreaticoduodenectomy between October 1994 and December 2002 were analyzed with regard to postoperative hemorrhagic complications. Delayed hemorrhage was defined as bleeding at the operation site after 5 or more postoperative days. RESULTS Delayed hemorrhage occurred in 22 patients (4.4%), with a median time of 13 days (range 7 to 32 days) after pancreaticoduodenectomy, and developed more frequently (9/77 versus 13/423, p = 0.003) in patients with preceding intraabdominal complications such as pancreatic fistula, bile fistula, and intraabdominal abscess. In 17 of these 22 patients, angiography and laparotomy revealed bleeding foci at 14 arterial and 3 anastomotic sites. In nine patients, hemorrhage developed from pseudoaneurysms of the major arteries around the pancreaticojejunostomy. Hemostatis was attempted by transcatheter arterial embolization in 14 patients and with laparotomy in 4 patients. Four of 14 patients who received transcatheter arterial embolization eventually required laparotomy. Overall, 4 of the 22 delayed hemorrhage patients died (18.2%) of complications related to massive bleeding or transcatheter arterial embolization. CONCLUSIONS Delayed hemorrhage after pancreaticoduodenectomy is associated with a high mortality. Intraabdominal complications after pancreaticoduodenectomy should be evaluated properly and guidelines for the diagnosis and treatment of delayed hemorrhage should be established in advance. Clinicians must be alert to the possibility of pseudoaneurysm hemorrhage.