In 5 patients with cirrhosis of the liver sulfated and nonsulfated [14C]cholic acid and [14C]chenodeoxycholic acid were administered intravenously and the specific activity curves were determined. Specific activities declined exponentially and pool sizes, synthesis rates, and turnover rates of bile acids were calculated on the basis of a one-pool system. The biological half-life of cholic acid was 4.3 +/- 1.6 days (mean +/- SEM) and of chenodeoxycholic acid was 2.8 +/- 1.2 days. The half-life of cholic acid sulfate was 0.7 +/- 0.5 day and of chenodeoxycholic acid sulfate was 0.8 +/- 0.5 day. The pool size of cholic acid was 513 +/- 103 mg, of chenodeoxycholic acid, 477 +/- 77 mg, of cholic acid sulfate, 4.7 +/- 1.0 mg, and of chenodeoxycholic acid sulfate, 38.7 +/- 4.0 mg. The daily synthesis of cholic acid was 90 +/- 14 mg, of chenodeoxycholic acid, 118 +/- 6 mg, of cholic acid sulfate, 7.2 +/- 2.1 mg, and of chenodeoxycholic acid sulfate was 32.6 +/- 3.2 mg. The data indicate that sulfate esters of bile acids are significantly more rapidly excreted than are unsulfated bile acids. More than one-fourth of the chenodeoxycholic acid but less than one-tenth of the cholic acid formed was sulfated. The preferential sulfation of chenodeoxycholic acid is responsible for the more rapid turnover of chenodeoxycholic acid in comparison to cholic acid. Sulfation enhances the excretion and thereby prevents the accumulation of hepatotoxic concentrations of chenodeoxycholic acid in patients with cirrhosis of the liver.