alpha-glucosidase inhibitors (alphaGIs) increase active glucagon-like peptide-1 (GLP-1) and reduce the total glucosedependent insulinotropic polypeptide (GIP) levels, but their ability to prevent diabetes remains uncertain. Dipeptidyl peptidase-4 (DPP-4) inhibitors, such as sitagliptin, increase active GLP-1 and GIP levels and improve hyperglycemia in a glucose-dependent fashion. However, the effectiveness of their combination in subjects with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT) is uncertain. The present study evaluated the effect of miglitol, sitagliptin, and their combination on glucose, insulin and incretin levels in non-diabetic men. Miglitol and sitagliptin were administered according to four different intake schedules (C: no drug, M: miglitol; S: sitagliptin, M+S: miglitol and sitagliptin). The plasma glucose levels were significantly lower for M, S and M+S than for the control. The areas under the curve (AUCs) of the plasma active GLP-1 level in the M, S, and M+S groups were significantly greater than that in the control group. The AUC of the plasma active GLP-1 level was significantly greater for M+S group than for the M and S groups. The AUC of the plasma total GIP level was significantly smaller for M+S group than for the control and M and S groups. The results of our study suggest that miglitol, sitagliptin, or their combination contributes to the prevention of type 2 diabetes.