Currently 17 million Americans have diabetes mellitus (DM); 90% of these have type 2 DM. Of these 17 million, 5.9 million remain undiagnosed. The undiagnosed patient with type 2 DM may be asymptomatic for years, while hyperglycemic injury to target organs occurs long before the development of frank diabetes. The prevalence of diabetes among adults is estimated to increase to almost double the present number by 2025. People with diabetes and at risk for diabetes are also at risk for cardiovascular disease. Several investigators have now demonstrated the benefit of controlling blood glucose levels as well as other risk factors in this population to decrease the incidence of microvascular and macrovascular disease. Prevention or delaying the onset of type 2 DM can be accomplished with a program of diet, weight loss, and exercise.