Because of its favorable pharmacological properties, combination of a DPP-4 inhibitor, metformin, and thiazolidinedione has been increasingly used to achieve rapid glycemic goal with low risk of hypoglycemia and no weight gain, and to delay the need for subsequent regimen changes. DPP-4 inhibitors block DPP-4 enzyme and preserve endogenous incretins whereas metformin increases the active form of GLP-1, both of which may enhance the secretory function of pancreas. However, the response to DPP-4 inhibitors and metformin combination therapy may be different in individuals according to their pancreatic function and insulin resistance status. In fact, previous studies with DPP-4 inhibitors showed different potency in glycemic controls depending on various patient characteristics including severity of diabetes and the use of other antidiabetic drug.Consequently, it would be clinically important to investigate effect of this triple combination therapy.