1. Xamoterol (Corwin, Carwin, Corwil, Xamtol, ICI 118,587), a beta 1-adrenoceptor partial agonist, improves both systolic and diastolic function in heart failure patients. 2. Double-blind, randomised studies comparing xamoterol with placebo showed that the beneficial haemodynamic effects of xamoterol produced significant improvements in exercise capacity and symptoms in patients with mild to moderate heart failure. These studies formed the basis for a large European multicentre study programme which recruited over 1000 patients, randomised to xamoterol (200 mg twice daily, n = 617), digoxin (0.125 mg twice daily, n = 135) or placebo (n = 300) for 3 months. 3. Efficacy was assessed by measuring exercise capacity and symptoms. The xamoterol group improved exercise capacity by 37% compared with an 18% improvement in the placebo group. Differences in the symptom scores measured by visual analogue scales and Likert scores indicated significant improvements by xamoterol in the cardinal symptoms of heart failure, dyspnoea and fatigue. 4. Analyses of data from subsets of patients in the study showed that elderly patients, patients on no other heart failure therapy and patients with cardiomegaly all had similar improvements in exercise and symptoms to those seen in the whole study population. In the subset which included digoxin treatment, xamoterol produced significantly greater improvements in exercise capacity than digoxin (33% vs 17%, P less than 0.05) and was associated with fewer side-effects. 5. Xamoterol is therefore a promising addition to heart failure therapies currently available.