The effect of deoxycholate ingestion, 750 mg per day, on bile acid kinetics, biliary bile acid composition, and biliary lipid secretion was studied in 7 healthy volunteers. Bile acid kinetics were measured by isotope dilution, and hourly outputs of bile acid, cholesterol, and phospholipid were quantitated by a duodenal perfusion technique during a 24-hr period which included three liquid meals and an overnight fast. Biliary bile acid composition was assessed by coupled gas chromatography-mass spectrometry. After deoxycholic acid ingestion, biliary bile acids became composed of predominantly deoxycholyl conjugates, and deoxycholic acid pools increased 4-fold. Both chenodeoxycholic and cholic acid pools decreased, and daily synthesis of each of the primary bile acids was inhibited by 50%. Total bile acid pools did not change in any consistent manner. Daily bile acid secretion increased slightly during deoxycholic acid ingestion, and recycling frequency varied reciprocally with the total bile acid pool both before and during deoxycholic acid treatment. Deoxycholic acid ingestion caused no change in either the daily secretion of cholesterol or lecithin, or the cholesterol saturation of fasting-state bile, which remained unsaturated throughout the study. SGOT levels increased to 4 times the upper limits of normal in 2 of 7 subjects, but these levels promptly returned to normal when deoxycholate feeding was stopped. Serum cholesterol levels decreased in every subject (average 15%) during deoxycholic acid administration. No evidence for a direct role of deoxycholate in the pathogenesis of cholesterol cholelithiasis was obtained in these studies.