Xamoterol is a beta-adrenoceptor partial agonist which selectively acts at the beta 1-receptors of the heart. The partial agonist effect modestly increases myocardial contractility and appears also to improve diastolic function and cardiac output without an increase in myocardial oxygen demand. Improved myocardial performance is maintained during exercise while increased heart rate is attenuated. Partial agonist activity protects against tachyphylaxis and arrhythmogenicity. With chronic treatment, exercise duration and work capacity increase and clinical manifestations of heart failure are reduced.