Vildagliptin is a new oral antidiabetic agent that enhances pancreatic islet cell responsiveness to glucose. An extensive clinical program involving approximately 22,000 patients and 7000 patient-years of exposure to vildagliptin has shown that the agent is well tolerated and effi cacious in improving glycemic control in patients with type 2 diabetes mellitus (T2DM). Monotherapy trials have shown that signifi cant HbA1c lowering is accompanied by body weight-neutral and lipid-neutral effects, low risk of edema, and low risk of hypoglycemia. These characteristics make vildagliptin a favorable partner for combination therapy. Studies of vildagliptin as an add-on to metformin have shown signifi cant improvements in glycemic control (comparable to that of thiazolidinedione add-on), with the combination being well tolerated and associated with low risks for hypoglycemia and adverse effects on weight or lipid levels. Good tolerability and clinically relevant improvements in glycemic control have also been observed with vildagliptin as an add-on treatment to sulfonylurea, thiazolidinedione, or insulin treatment or in initial combination treatment with pioglitazone. Improved β-cell function and glycemic control have been shown with vildagliptin in subjects with impaired glucose tolerance and in T2DM patients with mild hyperglycemia, with some evidence in the latter suggesting the potential for modifying disease course. Keywords: diabetes, vildagliptin, incretin, metformin, add-on treatment, hypoglycemia Type 2 diabetes mellitus (T2DM) is a dual disease, characterized by islet (beta-and alpha-) cell dysfunction in the setting of insulin resistance. Moreover, ample clinical evidence, such as data from the landmark UK Prospective Diabetes Study (UKPDS), indicates that loss of beta-cell function is progressive. This progressive decline leads to the clinical impression of failure of therapy in T2DM patients and is the main reason why so many patients with T2DM are not within target ranges of glycemic control. Moreover, the clear alpha-cell dysfunction that is also present in T2DM has been disregarded in previous years, mainly because therapeutic interventions were lacking. The need to address this underlying islet cell defi cit led to a search for therapeutic alternatives and has led to the rediscovery of the incretin hormones and their role in glucose homeostasis. Improved understanding of their potential has led in turn to the development of incretin analogs and incretin enhancers for treatment of T2DM (Deacon 2004;Vilsbøll and Holst 2004;Drucker 2006;Deacon et al 2008).The present review will discuss the data available on the incretin enhancer vildagliptin, a potent and selective inhibitor of dipeptidyl peptidase-4 (DPP-4), the enzyme responsible for the rapid degradation of the incretin hormones glucagonlike peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). This activity increases levels of active incretins and enhances pancreatic islet α-and β-cell responsiveness to glucose, thus improving ...