Metformin has now been established as the drug of choice for the first-line management of type 2 diabetes mellitus. It reduces insulin resistance, improves glycaemic control, and can be safely combined with other classes of oral hypoglycaemic agents. Equally important, metformin has been shown to have a significant beneficial effect on cardiovascular morbidity. Moreover, this agent acts favourably on blood pressure, lipids, haemostasis and other features of the metabolic syndrome. Metformin also contributes to weight reduction and diabetes prevention.