The α-glucosidase inhibitor voglibose (AO-128) was designed to prevent rapid postprandial blood glucose rises in non-insulin-dependent diabetics. We analyzed its effect on the entero-insular axis in 72 healthy volunteers in a double-blind study design before, after the 1st dose, and on the 7th day of a 7-day treatment protocol (3 daily loads). Six parallel groups of 12 volunteers received voglibose (0.5, 1.0, 2.0, or 5.0 mg) or placebo (two groups). Blood was drawn at regular intervals up to 180 min after a standardized breakfast to analyze the levels of glucose, insulin, C peptide, gastric inhibitory polypeptide, and glucagon-like peptide 1 (GLP-1). As expected, after ingestion of voglibose, slight to moderate gastro-intestinal discomfort but no severe side-effects were reported. In a dose-dependent manner, voglibose significantly reduced postprandial increases of blood glucose, insulin, and C peptide. At the lower loads (0.5 and 1 mg voglibose three times daily), these effects were more pronounced after 7 days. The postprandial increase of gastric inhibitory polypeptide was already reduced after the first load of 2 and 5 mg voglibose. In comparison to the placebo group, this inhibition became also significant for the lower loads after 7 days. Interestingly, GLP-1, originating from the lower intestines, was increasingly released under voglibose treatment. The first administration of 1 mg voglibose enhanced GLP-1 secretion > 80% above controls. Treatment with 1 mg voglibose three times daily over 7 days revealed a maximal mobilizing effect on endogenous GLP-1 ( > 90% above controls) which was not further increased by 2- or 5-mg loads. We conclude that voglibose treatment effectively inhibits intestinal disaccharidases and thereby mobilizes the endogenous pool of insulinotropic GLP-1.