Regurgitation of bile, pancreatic juice, or duodenal secretions into the stomach or esophagus occurs under certain conditions and has been incriminated as the cause of gastritis and alkaline esophagitis. In an experimental study in dogs, bile was diverted into the stomach and into the ileum for four months without producing substantial mucosal changes. In similar experiments, pancreatic juice was diverted into the stomach and colon for 1 to 12 months, again without producing mucosal damage. The parenchyma of the spleen and kidney was exposed to concentrated gallbladder bile for long periods without causing substantial changes. These findings suggest that individual duodenal secretions produce little or no damage on contact with the gastrointestinal mucosa of the dog or on the parenchyma of the spleen or kidney.