Burgeoning obesity is increasing the prevalence of type II diabetes mellitus. As a consequence, there will be an even greater burden of cardiovascular disease, end-stage renal disease, blindness, and lower extremity amputations. If diagnosed, impaired glucose tolerance presents an opportunity for intervention that potentially could delay or prevent the development of diabetes. Recent prospective studies document the effectiveness of exercise and weight reduction in preventing diabetes. Metformin is less effective than intense lifestyle interventions. Acarbose, losartan, orlistat, pravastatin, ramipril, and hormone replacement therapy are associated with lower rates of the development of diabetes. The Diabetes Reduction Assessment with Ramipril and Rosiglitazone Medication (DREAM) trial and the Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) trial were designed to assess not only the prevention of diabetes but also the impact on cardiovascular morbidity and mortality.