Several classes of antihyperglycemic agents are available for the treatment of patients with type 2 diabetes. These agents, including thiazolidinediones, biguanides, insulin secretagogues, alpha-glucosidase inhibitors, and insulin, offer differing mechanisms of actions and can be used either alone or in combination. The thiazolidinediones are a newer class of oral antidiabetic agents that improve glycemic control and may preserve beta-cell function. Clinical trial data suggest that patients with type 2 diabetes experience progressive deterioration of beta-cell function. By decreasing insulin resistance, thiazolidinediones may preserve beta-cell function, and patients may experience prolonged glycemic control. The thiazolidinediones also exert beneficial effects on dyslipidemia, endothelial function, coagulation, and blood pressure. By improving these components of the metabolic syndrome, thiazolidinediones may reduce the incidence of both microvascular and macrovascular complications. This article provides an overview of the role of thiazolidinediones in the treatment of type 2 diabetes. (C) 2002 by Excerpta Medica, Inc.