The review summarizes the results of Norwegian investigations of gastric secretion and gastric secretory tests as a diagnostic procedure in peptic ulcer patients. The introduction of gastroscopy as a method of accurate diagnosis of gastric diseases made it less important to examine gastric secretory capacity in the clinical setting. The gastric secretory tests remain to be essential in defining the indications for and the impact of surgical interventions in intractable peptic ulcers. Gastric secretory studies are of great value in studying gastric physiology and pathophysiology and in evaluating the efficacy of the drugs that inhibit hydrochloric acid secretion.