Fasting serum concentrations of glycine and taurine conjugates of cholic, chenodeoxycholic, and deoxycholic acid were measured with a high-pressure liquid chromatography-enzymatic assay in patients with hepatobiliary disease. The total glycine to taurine ratio was significantly lower in extrahepatic cholestasis (median 1.1) than in cirrhosis (median, 2.0) and controls (median, 1.7). In patients with cirrhosis the ratio was significantly correlated with the S-bilirubins, P-coagulation factors (II + VII + X), and S-total conjugated bile acids. Because of large overlaps of the ratio between the groups the glycine to taurine ratio is of hardly any diagnostic value. The ratio of cholic acid conjugates to chenodeoxycholic acid conjugates was over 1.5 in 10 of 12 cholestasis patients and below this value in all but 1 patient with cirrhosis; the separation of the groups was not improved by splitting the ratio in glycine and taurine conjugates. This study does not suggest that separate determination of glycine and taurine conjugates of bile acids in serum adds diagnostic information in hepatobiliary disease.