As the number of type 2 diabetes patients is still increasing in Japan, careful management and appropriate treatment of diabetes with oral hypoglycemic agents are required for all general physicians. Ultimate aim of treatment should be maintenance of a quality of life not different from that of persons without diabetes. Recently various new oral hypoglycemic agents have been developed and six different classes of agents are available now: sulfonylureas, biguanides, alpha-glucosidase inhibitors, glinides, thiazolidinediones, and dipeptidyl peptidase-4 inhibitors. In this article we describe the specific mechanisms of actions, side effects, and important points in clinical usage. Every drug therapy should be supported by lifestyle changes and the agents to be used should be selected after consideration of patient's patho-physiological state of diabetes, the presence of any complications, age, functional disorders of the liver, kidney, heart and lung, and the risk for hypoglycemia.