Although beta-adrenoreceptor antagonists appear to be beneficial in chronic heart failure there is little information on their effects on autonomic and baroreceptor function which may have important prognostic implications. We sought to determine first whether beta-adrenoreceptor blockade will improve baroreceptor function and vagal tone in chronic heart failure, and second whether there were any differences between standard therapy with metoprolol and the second-generation vasodilating beta-blocker celiprolol. In this double-blind randomized placebo-controlled study 50 patients with stable chronic heart failure received either celiprolol 200 mg daily, metoprolol 50 mg twice daily or placebo for 12 weeks after a 4-week dose titration period. Thirty-five healthy normal subjects were also studied. Baroreceptor gain was assessed non-invasively by cross-spectral analysis of R-R and systolic blood pressure low- and high-frequency components (the alpha angle) during controlled respiration. High-frequency power was used as a measure of vagal modulation. Satisfactory recordings for analysis were obtained in 31 patients with heart failure. The results showed that at baseline baroreceptor gain (alphaHF) was significantly depressed in patients with heart failure compared with the normal control group (4.95+/-0. 55 versus 11.73+/-1.32 ms/mmHg, P<0.0001). After 12 weeks of treatment with metoprolol baroreceptor gain improved significantly whether measured while supine (P=0.03) or standing (P=0.009), and this was associated with a significant increase in R-R HF power (P=0. 008). There were no significant changes after treatment with celiprolol or placebo. We conclude that metoprolol but not celiprolol therapy restores baroreceptor gain towards normal and increases vagal tone in chronic heart failure. The ancillary properties of celiprolol do not appear to provide any advantages over metoprolol for the restoration of autonomic and baroreceptor function in heart failure.