The purpose of the investigations was the determination of the maximum gastric secretion during hyperglycaemia in healthy subjects as well as in patients with short-term and long-term diabetes. After the stimulation with pentagastrine, given in the dose of 6 microgram per kg of body weight in 0.9% sodium chloride solution continuous intravenous infusion, there were determined MAO, parietal and nonparietal secretions, the concentrations of sodium, potassium, chloride, calcium and magnesium, and the total secretin of these electrolytes in gastric juice. In healthy subjects hyperglycaemia was induced by intravenous infusion of 30% glucose solution. Under the influence of hyperglycaemia the decrease of MAO (p less than 0.001) in healthy subjects as well as in diabetics was found. In healthy subjects the decrease of the total potassium, chloride and magnesium secretion in gastric juice (p less than 0.001) was observed. In patients with long-term diabetes the decrease of the secretion of sodium, potassium, chloride, magnesium and calcium was observed. There were no differences in gastric secretion in both groups of diabetics. The inhibitory effect of hyperglycaemia on the parasympathetic system and the decreased release of endogenous gastrine may be the causes of these changes. Insulin may also inhibit gastric secretion.