The concentration of bile acids in serum was measured by an enzymatic-fluorometric method under fasting conditions and 2 hours after a standardized meal in 26 patients with chronic liver disease (chronic hepatitis, liver cirrhosis, primary biliary cirrhosis) and compared with other tests of liver function. Postprandial bile acids and transaminases were false negative in only 12% and are thus the most sensitive tests after the BSP-retention test (3% false negative results). In comparison, fasting bile acids proved to be a relatively insensitive screening test for liver disease (38% false negative results). Postprandial bile acids were more closely correlated with BSP retention and BSP disappearance rate constant (Ki) than fasting bile acids. In view of these findings postprandial serum bile acid concentrations should be preferred to fasting bile acid concentrations in screening for liver disease and monitoring liver function.