25 patients suffering from different hepatic diseases were studied in order to investigate the elimination of the beta-receptor blocking drug pindolol in hepatic disease. Following an overnight fasting period the patients received simultaneously 3 mg pindolol intravenously and 1000 mg antipyrine orally. Plasma samples were taken at certain time intervals for 24 hs and urine was collected for 72 hs for the measurements of drug concentrations in plasma and urine. From these measurements different pharmacokinetic parameters were calculated for both drugs used in the present study according to a one-compartment open model. The total body clearance of antipyrine was selected as a parameter of the metabolic capacity of the liver microsomal enzyme system and was compared with the pharmacokinetic parameters calculated for pindolol by means of linear regression. There was no significant correlation between the total body clearance of antipyrine and the kinetic parameters of pindolol in any of the 25 patients irrespective of the differences in liver disease. On the other hand, 14 patients suffering from cirrhosis of the liver showed a significant correlation between the total body clearance of antipyrine and the overall elimination rate constant or metabolic clearance of pindolol. No correlation was found between antipyrine clearance and total body clearance of pindolol, as some patients with intact renal function excreted a higher proportion of pindolol in the urine as liver function decompensated. The mechanism of such compensatory elimination is unknown. In conclusion, the total body clearance of antipyrine known to represent metabolic liver function showed a significant correlation with the metabolic clearance of pindolol in patients with cirrhosis of the liver. For the other liver diseases investigated, too few patients were studied to calculate an adequate correlation.