A large number of individuals currently diagnosed as having diabetes mellitus are asymptomatic. In order to provide rational therapy for this patient population, it is necessary to focus upon the differences between these patients and the classic prototypes with polyuria and weight loss, who require insulin for survival. Patients with asymptomatic diabetes do not need insulin for survival, and, by definition, they do not need it to alleviate symptoms. They tend to be middle-aged and overweight, but they can be young and thin. Their degree of hyperglycemia is moderate, often indistinguishable from that of normal individuals in their day-to-day existence. Indeed, they can often be differentiated from normal persons only on the basis of their blood glucose response to the stress of a large dextrose challenge; in this regard, the potential problem of over-diagnosing diabetes has been discussed. Since the major problem facing patients with asymptomatic diabetes is accelerated atherogenesis, the therapeutic approach must be based upon efforts to delay or prevent the onset of vascular disease. It has yet to be shown that any therapeutic intervention helps such patients, but an argument has been made in support of the following goals in subjects with asymptomatic diabetes whose fasting blood glucose level is less than 170 mg/100 ml: (1) stop smoking, (2) control hypertension, (3) attain ideal body weight, and (4) maintain blood triglyceride and cholesterol levels well within normal limits. Attempts to lower blood glucose with either insulin or oral agents do not seem indicated in the majority of patients within this defined diabetic population.