Resting heart rate is a well recognized marker of autonomic nervous system tone, and in many population studies has been found to be a significant correlate of blood pressure, increased body mass index, and metabolic disturbances. This association is particularly striking in patients with hypertension or diabetes, and cardiovascular morbidity related to high heart rate in these conditions seems to depend mainly on the clustering of these risk factors. The prospective relationship between tachycardia and metabolic abnormalities found in longitudinal studies indicates that the adrenergic overdrive is the cause rather than the consequence of the insulin resistance state. Findings from observational studies and clinical trials have shown that heart rate measured during the follow-up provides prognostic information over and above heart rate measured at baseline, whereas the predictive value of heart rate measured out of the office is still debated. Antihypertensive drugs that decrease blood pressure and heart rate through a reduction of the sympathetic outflow may be more beneficial in clinical situations characterized by heightened sympathetic activity associated to insulin resistance.