**1. Introduction**

Discovery of incretin hormones and their role on glucose metabolism and pathogenesis of type 2 diabetes mellitus (T2 DM) are current interests of diabetology. Incretin hormones are secreted from intestinal endocrine cells in response to food ingestion and potentiate pancreatic insulin secretion when compared with iv glucose administration. Since malfunction of incretin hormones has been found to have role in T2 DM pathogenesis, incretin based therapies have been developed. Incretin effect, incretine hormones, functions, their role in pathogenesis of T2 DM and management of T2 DM with incretin-based drugs are discussed in this chapter.
