The purpose of this study is to evaluate the diagnostic value of the following tests in the assessment of patients with chronic liver disease (CLD) and cholestatic syndrome (CS): (1) aminopyrine breath test, measuring 14CO2 excretion in the expired air, (2) peripheral clearance of [99mTc]EHIDA, and (3) postprandial levels of glycocholic acid (GCA) and glycochenodeoxycholic acid (GCDCA). The results indicate that: (1) 14CO2 2-hr excretion rate is a specific and sensitive marker of liver function, with good correlation with postprandial bile acid levels, [99mTc]EHIDA retention, and the conventional tests of serum albumin and prothrombin time. (2) Peripheral clearance and retention of [99mTc]EHIDA increased in both groups of CLD and CS vs controls, but it does not discriminate between the two. (3) Postprandial bile acids were elevated in CLD, particularly those of GCDCA, whereas GCA levels were significantly elevated in CS compared with CLD. This may be due to increased synthesis and entry into the blood. (4) The combination of [14C]aminopyrine breath test and postprandial levels of GCDCA enhance the diagnostic value, specificity, and sensitivity in the assessment of patients with CLD.