The pattern of serial serum bile acid and bilirubin concentrations in 3 patients with benign recurrent intrahepatic cholestasis (BRIC) was compared with those from patients with other liver diseases. In BRIC the peak bile acid concentration (260- 575 micromol/l was found at the onset of the cholestasis. The bilirubin concentration increased slowly so that maximum values (185-550 micromol/l) were attained between 33 and 51 days after the onset of symptoms. Both the serum bile acid and bilirubin concentrations returned to normal after 79 to 98 days. Percutaneous biliary drainage of extrahepatic biliary obstruction (3) caused a dramatic reduction in the serum bile acid level (mean 89% after 48 hours), but only a slight fall in serum bilirubin (mean 22%). In primary biliary cirrhosis (2) the bile acid and bilirubin concentrations changed in parallel until the onset of liver failure when serum bilirubin, but not bile acids, increased markedly. Serum bile acid and bilirubin concentrations changed in parallel throughout cholestatic viral hepatitis (2), chronic active hepatitis (2) and alcoholic hepatitis (1). The data indicates that a distinctive pattern is found in BRIC and this may be of diagnostic value.