This was a double-blind, randomized, prospective study comparing the effects of nebivolol and atenolol on systolic diastolic left ventricular function in patients with essential hypertension. A significant difference was seen in stroke volume between these 2 drugs. The blood pressure lowering effect of atenolol was strongly related to cardiac output and heart rate reduction. The blood pressure lowering effect of nebivolol was related to a reduction in peripheral resistance and an increase in stroke volume with preservation of cardiac output. This preservation of cardiac output, together with a reduced peripheral resistance, may be potentially important in treating heart failure.