Taurine concentration in liver biopsies taken from 20 patients undergoing cholecystectomy or laparotomy for obstructive jaundice correlated with percentage of taurineconjugated bile acids in hepatic bile. In biliary obstruction, taurine concentrations in muscle did not parallel high hepatic taurine concentrations, suggesting selective hepatic taurine accumulation in biliary obstruction. In fasting subjects with an intact bile acid enterohepatic circulation, per cent taurine-conjugated bile acids in bile was the same as per cent taurine conjugation of bile acids by the liver. Ingestion of small amounts of taurine (250 mg) can increase the per cent taurine conjugation by the liver. Of 10 subjects, 7 increased per cent taurine conjugation of bile acids by the liver by 2.5 to 10% at 2½ hr after intraduodenal taurine administration. We conclude that hepatic taurine concentration is a major determinant of per cent taurine conjugation of bile acids by the liver in man. In the fasting subject with an intact enterohepatic circulation, per cent taurine-conjugated bile acid in the bile acid pool is very close to the per cent taurine conjugation of bile acids by the liver. Hepatic bile acid conjugation pattern may differ from that of the bile acid pool as a result of taurine ingested with meals, but the deviation is small, and acute alteration of the per cent taurine conjugation in the bile acid pool does not occur.