Now seven compounds of DPP-4 inhibitor are available in Japan. They can be used in any stage of type 2 diabetes if the insulin secretion capacity is retained; first-line choice to third-line choice or combination with insulin therapy. There is no apparent difference in effect of each DPP-4 inhibitor on glycemic control; HbA1c levels are decreased by 0.6- 1.0% by monotherapy. Generally the drug is more effective for improving glycemic control in Japanese population compared to that in Western population. In addition, basal insulin therapy could be switched to the combination therapy with DPP-4 inhibitor and sulfonyl- urea in Japanese type 2 diabetes in cases where insulin secretion capacity is sufficiently preserved. Here we summarize the effect of DPP-4 inhibitor on glycemic control and algorithm for DPP-4 inhibitor treatment.