Well designed intervention trials, such as the Diabetes Prevention Program (DPP), have demonstrated the potential of lifestyle interventions or pharmacologic treatments for the prevention or delay of type 2 diabetes in subjects with impaired glucose tolerance (IGT). Lifestyle interventions are likely to form the cornerstone of the management of IGT in the future, as they do in the management of type 2 diabetes today. However, it remains to be seen whether the intensive lifestyle interventions employed in trials such as the DPP can be transferred successfully from the highly structured environment of a randomised trial to routine, day-to-day management within the primary care sector. Thus, pharmacologic treatment may provide an important additional option where subjects are unwilling or unable to improve their diet and levels of physical activity. Treatment with metformin significantly reduced the incidence of diabetes in subjects with IGT and high-normal fasting plasma glucose in the DPP. Moreover, metformin was well tolerated, and health economic analyses suggest that metformin treatment is cost-effective in the US and Europe. The DPP investigators found that the protective effect of metformin persisted beyond the end of the study, and estimated that only one quarter of the protection arose from a short-lived pharmacological effect. The results of the DPP identify metformin as an effective option for the prevention of diabetes in subjects with IGT and impaired fasting glucose.