Patients with type 2 diabetes mellitus have a 2- to 4-fold increased risk of coronary heart disease (CHD) and a 4-fold increase in mortality from CHD. Intensive glycemic control has a more modest effect on reducing macrovascular complications than microvascular complications. Most likely, this is because the development of cardiovascular disease is multifactorial, and hyperglycemia is 1 of many risk factors. Epidemiologic data suggest that a glycosylated hemoglobin (A(1c)) level of < or =7% is reasonable to avoid or minimize the complications associated with type 2 diabetes. Studies have shown that there is an increased risk of cardiovascular mortality before the onset of type 2 diabetes. The presence of CHD before the onset of clinical diabetes provides strong evidence for a strategy of diabetes prevention in at-risk patients. Data indicate that the atherogenic pattern of changes in the prediabetic state is seen primarily in insulin-resistant patients rather than in those with abnormally low insulin secretion. Therefore, strategies to prevent or treat type 2 diabetes should focus on improving insulin sensitivity. Clinical trials have demonstrated that lifestyle changes (e.g., diet and exercise) as well as use of metformin, acarbose, or troglitazone reduce the incidence of type 2 diabetes. Prevention of type 2 diabetes may be an important strategy to delay or prevent cardiovascular disease in many individuals.