This contribution reviews briefly the history of the discovery and cha
racterization of peptic activity; secretory models and current concept
s regarding the regulation of pepsinogen secretion; and evidence that
pepsin is a necessary co-factor for gastroduodenal mucosal injury. Sev
eral animal studies indicate that peptic activity is required for acid
- and nonsteroidal anti-inflammatory drug-induced gastroduodenal ulcer
ation. A more vigorous approach to the development of anti-peptic drug
s for the treatment of peptic ulcer disease is encouraged.