Xamoterol is a beta-1 selective partial adrenoceptor agonist. Thirty patients (one female, 29 male, mean age 56 +/- 8 years) with coronary artery disease and mild to moderate heart failure, according to NYHA classes II and III, were studied before and 15 min after intravenous administration of 0.2 mg/kg xamoterol, at rest and during standard, supine bicycle exercise. At rest, the pulmonary capillary wedge pressure fell by 39% (p = 0.0001) and the cardiac index increased by 7% (p = 0.0084); heart rate increased only slightly. With exercise, cardiac index did not change and the pulmonary capillary wedge pressure decreased by 11% (p = 0.0003). In addition, the heart rate dropped from 115 to 105 bt/min (p = 0.0001) which resulted in a decrease of the rate pressure product by 9% (p = 0.0041). Arterial blood pressure remained unchanged. Norepinephrine plasma levels did not change at rest or during exercise, whereas at rest plasma renin activity dropped by 18% (p less than 0.05) and by 20% (p less than 0.05) during exercise. No untoward side effects were observed and the drug was well tolerated. In conclusion, xamoterol, given acutely to patients with heart failure NYHA classes II or III exerted advantageous hemodynamic effects at rest and during exercise.