Pantoprazole, a novel proton pump inhibitor, is a potent inhibitor of gastric acid secretion. In this review, data are presented from nine controlled, prospective, clinical pharmacodynamic investigations. The effects of oral and intravenous doses of pantoprazole (administered for 5-7 days) on continuously monitored 24-h intragastric pH and serum gastrin are discussed: oral pantoprazole 20 to 80 mg/day (given in the morning before breakfast) induced a dose-related increase in both the 24-h intragastric pH and the serum gastrin profile. The effects of pantoprazole doses of 60 and 80 mg were not significantly different from those of the 40 mg dose. It was concluded that oral pantoprazole at 40 mg/day is the optimal antisecretory dose for the treatment of acid-related diseases. In two comparative studies, this dose of pantoprazole (administered before breakfast) proved to be significantly more effective than ranitidine 300 mg (given in the evening) and omeprazole 20 mg (given in the morning). Administration of oral and intravenous pantoprazole (40 mg) was found to be equipotent at increasing 24-h intragastric pH, but this finding requires further evaluation. The approximately 2-4-fold rise in median serum gastrin concentrations following several days' administration of pantoprazole 40 mg is of a comparable magnitude to that of other proton pump inhibitors. It seems unlikely that this moderate hypergastrinaemia during pantoprazole treatment should influence the human enterochromaffin-like (ECL) cell density in a clinically relevant way, but data during long-term therapy are necessary to confirm this conclusion.