It is well established that inhibition of dipeptidyl peptidase (DPP)-IV reduces glucose levels and preserves pancreatic beta cell function in patients with type 2 diabetes. DPP-IV inhibitors stimulate insulin secretion as well as insulin biosynthesis and inhibit glucagon secretion from pancreas by increasing incretin (GLP-1) levels. Recent studies reported that combination therapy with DPP-IV inhibitors and other oral antidiabetic medication have additive or synergistic effects in lowering glycose level, preserving beta-cell mass and function as well as enhancing insulin sensitivity. However, there have been few studies about the glucose lowering effect of DPP-IV inhibitors in patients with type 2 diabetes on insulin treatment.