Among 70 cases of perforated duodenal ulcers treated by plication, eight were complicated by massive postoperative hemorrhage from a syncronous posterior "kissing" duodenal ulcer. Critical analysis revealed that only signs of gastrointestinal (GI) bleeding preoperatively had predictive value for postoperative hemorrhage. Twenty-four patients had one or more predictive signs, and eight actually bled postoperatively. There was a 50% mortality and 75% additional complication rate for the bleeders. In contrast, the nonbleeders had a mortality and a complication rate of only 18% and 35%, respectively. There was no observed superiority of either surgical or medical treatment for postoperative hemorrhage. In perforated duodenal ulcer with evidence of GI blood loss, an intraoperative search for a posterior kissing ulcer is recommended. If a kissing ulcer is found, an acid-reducing operation and suture ligation of the ulcer is indicated.