One group of 8 patients with primary biliary cirrhosis and one group of 7 patients with common duct stone both had generally high levels of blood coagulation factors and a wide range of other plasma proteins. In contrast, one group of 6 patients with chronic active hepatitis generally had low levels of the same coagulation factors and plasma proteins. Analyses of factor II-VII-X, plasminogen, ceruloplasmin, beta1C/1A-globulin, IgG and IgM are especially helpful in the differentiation between primary biliary cirrhosis and chronic active hepatitis. The data are interpreted as suggesting a generally increased synthesis of liver-produced proteins in cholestasis, although more specific factors may modify the degree of increase of the individual proteins.