Background: Vildagliptin, a potent and selective dipeptidyl peptidase-4 (DPP-4) inhibitor, increases the availability of endogenous incretin hormones, glucagon-like peptide (GLP-1), and glucose-dependent insulinotropic polypeptide, thereby improving glycemic control. The objective of this study is to further investigate the insulin sensitizing properties of Vildagliptin in comparison to those of Teneligliptin.Methods: Naive subjects with T2DM were administered 50-100mg/day Vildagliptin monotherapy (n = 53). As a comparator, monotherapy, 20mg/day Teneligliptin monotherapy was performed in a non-randomized manner (n=58). No other drugs were administered. At 3 month, levels of diabetic parameters were compared with those at baseline.Results: At 3 months, while similar reductions of glycated hemoglobin (HbA1c) levels were observed with these two drugs, indexes for insulin sensitivity homeostasis model assessment (HOMA)-R ameliorated only with Vildagliptin. Then, the subjects were divided into two groups representing distinct degrees of insulin resistance; high HOMA-R (C4) and low HOMA-R (2) groups. With Vildagliptin, similar decreases of HbA1c levels were observed in high (10.85-8.66%, p\0.0005) and low (11.12-8.91%, p\0.01) HOMA-R groups. HOMA-R (-31.9%, p\0.05) and non-high density lipoprotein cholesterol (non-HDL-C, -7%, p\0.05) levels significantly decreased. HOMA-B levels increased in both groups with significant inter-group differences (102.1 % in low HOMA-R group vs. 53.4 % in high HOMA-R group). Group 2. With Teneligliptin similar decreases of HbA1c levels were observed from those of vildagliptin in either high or low HOMA-R group, but no changes of HOMA-R, non-HDL-C levels were noted. Increases of HOMA-B levels with teneligliptin were comparable to those with vildagliptin in either high or low HOMA-R group.Conclusions: These results indicate that vildagliptin ameliorates insulin sensitivity and non-HDL-C levels in subjects with high degrees of insulin resistance and vildagliptin also shows glycemic efficacy by decreasing HbA1c. This is not the case with teneligliptin though similar glycemic efficacies were observed.