Abstract: Disclosed are methods employing compositions composed of unique mixtures of phospholipids and neutral lipids to treat the luminal lining of the gastrointestinal tract in the prevention or treatment of ulcerogenic processes such as peptic ulcer disease and inflammatory bowel disease. Compositions including mixtures of saturated or unsaturated phospholipids, together with saturated or unsaturated triglycerides and/or sterols, are shown to provide a surprising ulcer protective efficacy in experimental models. Further enhancement of activity is found upon the addition of a polyvalent cation or antioxidant to the various lipid mixtures.The present invention also discloses unique methods employing mixtures of phospholipids and neutral lipids for surfactant replacement therapy in the treatment of the various forms of respiratory distress syndrome. These compositions are shown to greatly enhance the surfactant replacement efficiency of surface-active lipids.