&NA;Studies in the past year have clarified several aspects of gastroduodenal defense. An explanation for the mucus layer's ability to allow free passage of secreted acid while acting as a barrier to luminal acid has been suggested. Further insights have been gained into the role of surface‐active phospholipids in defense and the regulation and actions of mucosal bicarbonate. Microcirculatory mechanisms of defense and injury, including the complex roles of nitric oxide, sensory afferent nerves, mast cells, and neutrophils, and the coupling of blood flow to acid secretion have been further elucidated. Other elements of the mucosal immune system, such as macrophages, plasma cells, and cytokines, have been found to modulate both defense and injury. Finally, progress has been made in better understanding the actions of a number of growth factors in mucosal defense and repair.Current Opinion in Gastroenterology 1993,9:902‐908