The selective beta 1-adrenoceptor antagonist metoprolol is eliminated primarily by hepatic metabolism and usually less than 5% of an oral dose is excreted unchanged in the urine. The effects of impaired liver function on the pharmacokinetics of metoprolol were studied in 10 patients with hepatic cirrhosis. All subjects were given single doses of 20mg intravenously and 50mg orally on separate days. The mean fraction of the drug available systematically was 84 +/- 10% in patients and 50 +/- 11% in a control group of 6 healthy subjects (p less than 0.05). The total body clearance of metoprolol in the cirrhotics was 0.61 +/- 0.13L/min and in the controls 0.80 +/- 0.11L/min. These values correspond to elimination half-lives of 7.2 +/- 1.2 and 4.2 +/- 1.1 hours, respectively. The differences were not statistically significant. Impaired liver function had no effect on the volume of distribution of metoprolol. Total clearance was weakly but linearly related to galactose clearance (r2 = 0.52; p less than 0.05), and the half-life was related to serum bilirubin (r2 = 0.74; p less than 0.01).