The resistance of the gastric mucosa to injury is attributable to a series of factors collectively known as "mucosal defense." Many components of mucosal defense are regulated by prostaglandins and nitric oxide (NO). Thus, inhibition of the production of these mediators predisposes the stomach to injury. Administration of these agents, as synthetic prostaglandins or NO donors, can restore mucosal defense and thereby prevent damage induced by several irritants. Repair of gastric ulcers is also influenced by NO and prostaglandins. Furthermore, a variety of growth factors appear to play critical roles in stimulating the formation of granulation tissue (the "foundation" for repair), the formation of new blood vessels, and the proliferation of epithelial cells. Better understanding of the factors that regulate ulcer healing should provide clues for the development of drugs that can produce better "quality" healing of ulcers.