alpha 2-PI, a coagulation factor, and AT III and PLG, fibrinolytic factors, are all glycoproteins synthesized in the liver, and their half-lives are as short as two to three days. Therefore, we assumed that determination of their plasma activities would be meaningful as a liver function test. We determined these three factors in 900 patients with various liver diseases and investigated their relation to serum biochemical data and differences in their activities among the diseases. Parameters in which all three factors were significantly correlated (magnitude of gamma greater than or equal to 0.5) were serum ALB, CHE and PT, indicating that the factors were suitable for the examination of liver function, particularly its reserve capacity. The activities of the three factors were significantly decreased (p less than 0.001) in the presence of acute hepatitis, chronic active hepatitis, fulminant hepatitis and liver cirrhosis. Compared with patients with compensated liver cirrhosis, those with decompensated liver cirrhosis exhibited significant decreases in the three factors. Among chronic hepatitis cases, the active type showed a more significant decrease in ATIII alone than the inactive type. These results indicate that determination of the three factors is very useful for the differential diagnosis and follow-up study of various liver diseases.