Variabilities on H+, Na+and K+concentration in gastric juice caused by Benzylimidazoline or Histamine dihydrochloride stimulation were studied on 215 patients with various diseases. Shifts on Na+and K+concentration in gastric mucous membrane by the same stimuli were also measured on both dogs and rats. The result was as follows. 1) A significant increase of total acidity and free hydrochloric acid acidity, a significant decrease of Na+concentration, and a slight increase of K+concentration in gastric juice were observed followed by either of stimuli. 2) Histamine causes a more effectable stimulation than Imidazoline on the three cation indicators. 3) Larger response was elicited with an increase of dose when Histamine was administered in a dose of 0.01, 0.02, 0.03, 0.04mg/kg. 4) A counter-correlation was observed between H+and Na+indicators on which the shifts were nearly as much. 5) When the patients were divided in three groups such as hypoacidity, normoacidity and hyperacidity which were determined from the basic secretion immediately before the stimulation, each group showed an approximation in time-course shift on each indiactors. 6) Other various stimulus-causing factors, chiefly consisted of insertion of gastric tube, seemed to play a relatively large role to the chemical stimulus per se, i.e. here is a problem of hypersensitivity on gastric mucous membrane. 7) From the view of diseases, the acidity is higher on the patients with doudenal ulcer and lower with gastric cancer. These two diseases, therefore, stand oppositely on Na+concentration. 8) Histamine stimulation in a dose of 0.04mg/kg caused a decrease of plasma Na+concentration and a increase of plasma K+concentration. 9) Plasma Na+and K+concentration have no correlation with the same indicators in gastric juice. 10) Na+and K+contained in gastric mucous membrane were found much more on pyloric resion than on corpus ventriculi. 11) An increased Na+concentration in gastric mucous membrane was observed in the animals previously treated with Ouabain only or Acetazolamide and Ouabain simultaneously.