Less attention has been devoted to the effects of antisecretory agents on pepsin secretion than to those on gastric acid secretion, particularly in human subjects. Moreover, comparison of the various trials is far from being simple and straightforward owing to the fact that the studies available present substantial variability in terms of types of subjects (controls, DU patients), gastric secretion (basal, stimulated), type of stimulation (pentagastrin, histamine, insulin, meals, sham feeding) antisecretory drug administration route (oral, i.v.) and considered parameters (concentration, output). This review of the published data reveals that all antisecretory agents reduce pepsin output, regardless of their sometimes very different mechanism of action. Despite this, there are differences in antisecretory effects according to the agent used to stimulate gastric secretion. Even within a single drug class (H2-antagonists, prostaglandins) there may be differences depending on the potency of the compound used.