The hemodynamic effects of CGP 17582 B, a new cardio-selective beta-blocking agent with moderate intrinsic sympathomimetic activity and minimal effects on myocardial contractility, were studied in patients after cardiac surgery for coronary artery bypass graft. Each patient had been treated preoperatively with beta-blocking agents and had a cineangiographic left ventricular ejection fraction between 40 and 60%. Fourteen patients were randomized to receive either 10 mg of propranolol or 50 mg of CGP 17582 B orally. Both drugs resulted in a significant and a similar decrease in heart rate. However, this was associated with a significant decrease in stroke volume after propranolol but not after CGP 17582 B, so that cardiac output significantly decreased only after propranolol. Thermodilution right ventricular ejection fraction significantly decreased after propranolol but not after CGP 17582 B. Each drug was well tolerated during the 10 following days and the recovery was uneventful in each patient. These results indicate that CGP 17582 B is a promising beta-blocking agent susceptible to reduce heart rate without altering cardiovascular function after cardiac surgery.