Several trials have demonstrated functional benefit with beta-blockers in patients with chronic heart failure. The aim of this observational study was to investigate if additional beneficial effects can be obtained from beta-blockade in a heart failure population that is already receiving high-dose ACE-inhibitor therapy. Atenolol is a long-acting cardioselective beta-blocking agent and is devoid of additional vasodilatory properties. Twenty-five male patients with class II or III heart failure and background therapy of digitalis, furosemide and 20 mg fosinopril per day were treated with 40 mg fosinopril per day and additional 75 mg atenolol per day (beta-blocker group) or with 40 mg fosinopril per day alone (control group). At the end of one year, changes in left ventricular function, exercise parameters and plasma neurohumoral variables reflecting vasoconstriction (noradrenaline, big endothelin) were measured and compared in the two treatment groups. Nineteen patients completed the study. Drop-outs were due to death (4 patients) and non-compliance (2 patients) with no significant difference between the groups. There was a beta-blocker related improvement in left ventricular ejection fraction (p < 0.05 between groups) and an increase in peak oxygen consumption in the control group only (p < 0.05 between groups). Thus, in a heart failure population receiving high-dose ACE inhibitor background therapy beta-blockade with atenolol produced additional benefit by reversing left ventricular dysfunction.