The clinical and pathological characteristics of Curling ulcer were defined by early and serial endoscopic examination of the duodenum in 37 burned patients. Duodenal disease was present in 27 patients and occurred only in patients with burns involving more than 38 percent of the total body surface. Erosive "duodenitis" could occur within 12 hours after injury and was usually associated with acute gastric disease. Isolated duodenitis occurred only in patients with pancreatitis. Contrast roentgenograms did not reliably show the superficial mucosal disease. Duodenal ulcerations were present in 12 patients and developed on a background of diffuse superficial mucosal injury. Other complications in the patient's postburn course influenced disease progression. Hemorrhage occurred in six patients with duodenal disease, usually originating from a posterior duodenal ulcer. Uncomplicated ulcers invariably healed within five weeks after diagnosis.