Beta-blocker use improves left ventricular ejection fraction (LVEF) in patients with heart failure. A similar effect of b blockers on right ventricular function has been proposed, although the effect of bisoprolol, a highly selective b-1 blocker, on right ventricular function has not been assessed. This study investigated the short-term effect of bisoprolol on right ventricular function in chronic heart failure patients. A cohort of 30 heart failure patients who were not taking b blockers at baseline was studied prospectively. Right ventricular ejection fraction (RVEF) and LVEF were measured at both baseline and 4 months by radionuclide angiography. Bisoprolol was up-titrated during four monthly visits by a preestablished protocol to a target dose of 10 mg/d. The dose of vasodilators was not changed. Quality of life and brain natriuretic peptide level were assessed. Mean age was 62.7+/-14.3 years. Baseline RVEF was 30.7%+/-6.3% and baseline LVEF was 21.7%+/-9.4%. Mean bisoprolol dose reached was 5.3+/-3.9 mg daily. At 4 months, RVEF significantly increased by 7.1% (95% confidence interval, 3.9-10.2; p=0.0001) and LVEF also increased significantly by 7.9% (95% confidence interval, 4.0%-11.9%; p=0.0003). Quality-of-life score improved from 42.8 to 30.8 (p=0.047). No correlation was found between brain natriuretic peptide levels and RVEF. Bisoprolol treatment for 4 months resulted in a significant improvement of RVEF, which paralleled the improvement of LVEF.