Vildagliptin is a potent and selective oral dipeptidyl peptidase-4 inhibitor that improves glycaemic control in patients with type 2 diabetes mellitus (T2DM) by increasing both alpha- and beta-cell responsiveness to glucose. The efficacy, tolerability and safety of the combination of vildagliptin and metformin in the treatment of T2DM have been established in numerous trials in the extensive vildagliptin clinical programme. As add-on therapy in patients with inadequate glycaemic control on metformin, vildagliptin produces clinically significant reductions in glycated haemoglobin (HbA1c) and fasting plasma glucose, is well tolerated, and is associated with absence of weight gain and minimal risk of hypoglycaemia. Compared with thiazolidinedione add-on treatment, vildagliptin is associated with similar significant reductions in HbA1c without the weight gain seen with the former. Compared with sulfonylurea add-on treatment, vildagliptin is associated with similar efficacy in controlling glycaemia but absence of weight gain and a markedly lower risk of hypoglycaemia. In drug-naive patients, single-tablet combinations of vildagliptin/metformin 50/500 and 50/1000 mg bid produced significantly greater reductions in HbA1c than monotherapy with either agent and were well tolerated, with no weight gain and minimal risk of hypoglycaemia. The combination of vildagliptin and metformin poses numerous advantages in the treatment of T2DM.