Glucagon-like peptide-1(GLP-1), an intestinal hormone secreted by L cells in response to luminal nutrients(carbohydrate and fat), enhances glucose-induced insulin secretion. Impairment of glucose-induced insulin secretion in patients with type 2 diabetes can be restored to near-normal by GLP-1 administration. In addition, GLP-1 possesses multiple biological effects which are favorable for the treatment of type 2 diabetes: inhibition of glucagon secretion, slowing of gastric emptying, reduction of appetite and food intake, upregulation of genes essential for insulin secretion(glucokinase, GLUT-2 etc), and beta cell proliferation and differentiation. Some long-acting GLP-1 derivatives which are resistant to the degradation by enzyme dipeptidyl peptidase-IV are currently under the clinical trial and are reportedly promising for the treatment of type 2 diabetes, because of impressive effects on glycemic control, availability by oral administration and very few adverse effects.