The influence of a single intravenous glucose load on maximal gastric acid secretion in 25 healthy men when stimulated with pentagastrin was studied. Under the influence of hyperglycaemia, a highly significant decrease of maximal acid output was found. Moreover, in the gastric juice an increase of chloride and calcium concentrations was noted. On the other hand, the output of potassium, chloride and magnesium was lowered. The above differences were statistically significant.