The behaviour of plasminogen (PLg) and plasminogen proactivator (PPLg) and some currently employed enzyme parameters were prospectively studied in 1047 subjects, of whom: 748 patients with liver diseases and jaundice; 52 tumor patients and 247 healthy persons. The patients with parenchymal liver diseases showed significantly reduced PLg and PPLg activity in direct relation with the severity and the stage of diseases. In patients with obstructive jaundice the activity of the fibrinolytic enzymes was usually normal, rarely increased. Other parameters such as: ALAT, LAP, G--GT and bilirubin were elevated most often in patients with viral hepatitis as well as in patients with obstructive jaundice. Quick time was found less affected during acute viral hepatitis and acute liver failure. It seems possible to recommend PLg and PPLg as liver function tests in association with the other function tests.