The hypoglycemic effect of a glycoside hydrolase inhibitor (BAY g 5421) was tested in 10 non-insulin dependent, overweight diabetics by means of continuous in vivo glucograms. There was a highly significant reduction of serum glucose with a dosage of 3 x 100 mg glycoside hydrolase inhibitor, after dosage division to 6 x 50 mg there was an additional reduction of blood glucose. This difference, however, could not be determined statistically. Insulin, glucagon and lactate as well as the triglyceride concentration remained unchanged. There were no significant side-effects. Two of the 10 patients complained of meteorism, after specific questioning three more patients offered similar complaints. Discontinuation of the preparation was not necessary.