This paper reviews the major advances made during the past year in understanding the ability of the gastroduodenal mucosa to resist injury. In particular, advances have been made in our understanding of the neural pathways and chemical messengers that mediate the hyperemic response to superficial injury; the regulation of gastric and duodenal bicarbonate secretion; the importance of mucus in mucosal defense and the physical properties that contribute to this role; the endogenous enzymes that prevent or reduce oxidant-induced injury; and the contribution of growth factors, polyamines, and prostaglandins to adaptive responses to injury.