Objective DPP-IV inhibitors are a new approach to treat type 2 diabetes. We designed this study to evaluated the effect of DPP-IV inhibitors on glucose control and islet function in Koreasn patients with type 2 diabetes. Methods 24 patients with type 2 diabetes were enrolled. Glucose, insulin and glucagon were measured during 75 g oral glucose tolerance test at baseline and after six month treatment with a DPP-IV inhibitor, sitagliptin. HbA1c was also checked. Results 75 g oral glucose tolerance test revealed a significant improvement in glucose control after sitagliptin treatment; glucose levels were significantly decreased at 60 minutes and 90 minutes (P＜0.05) and insulin secretion was concurrently enhanced overall (P＜0.05). However, glucagon secretion showed no significant changes. Changes of HbA1c were dependent on initial HbA1c; well controlled 11 patients whose initial HbA1c were less than 7% had little change (from 6.19±0.51% to 6.27±0.45%, P=0.567) but poorly controlled 13 patients whose initial HbA1c were above 7% had significant reduction (from 8.08±1.05% to 7.54±0.96%, P=0.0.35). Conclusion After six month treatment with a DPP-IV inhibitor patients with type 2 diabetes had enhanced postprandial glucose control and insulin secretion, which eventually brought improved overall glucose control. These changes were more prominent in poorly controlled patient.