To determine the effectiveness of hydrogen ion neutralization in preventing the clinical complications (hemmorrhage and perforation) of acute gastroduodenal disease after thermal injury, 48 patients with burns of greater than 35% total body surface were evaluated within 72 hours after injury. In a prospective, randomized fashion, patients were chosen to receive antacid or no-antacid therapy. An established lithiumflux technique was utilized to determine the integrity of the gastric mucosal barrier (GMB) before group selection. Only one of the 24 patients receiving antacid developed significant upper gastrointestinal bleeding; however, seven of 24 patients receiving no antacid experienced hemorrhage and gastric ulcer perforation (p less than 0.02). None of seven patients with GMB disruption who received antacid developed a clinical complication; however, six of 15 patients with GMB disruption receiving no antacid experienced clinical complications (p less than 0.05). Neutralization of gastric acid offers protection against the development of clinically significant ulcer complications in the burn patient.