This prospective, double-blind study used invasive monitoring and echo-Doppler techniques to compare the hemodynamic effects of nebivolol, a new beta1-selective beta-blocking agent with those of atenolol in patients recovering from coronary artery bypass grafting surgery. Five milligrams nebivolol and 50 mg atenolol equally decreased heart rate (HR) and blood pressure (BP) but, nebivolol, in contrast to atenolol, caused no decrease in stroke index (SI), cardiac index (CI), and right ventricular ejection fraction (RVEF). These differences appeared to be related in part to different peripheral effects of the two agents because nebivolol administration was associated with a reduction in systemic vascular resistance (SVR). After less-than-or-equal-to 10 days of treatment, acceleration of aortic flow velocity increased and isovolumic relaxation time decreased with nebivolol but not with atenolol treatment. Both drugs were equally well tolerated. Therefore, nebivolol shares most of its effects with classical beta1-blockers but is devoid of the potentially harmful effects on cardiac output (CO) and peripheral resistance.