According to the results of studying E.E.P. positive phenomena from the viowpoint of the properties of the serum, some E.E.P. positive cases were examined in order to consider the clinical significance of E.E.P. The results were follows: 1. E.E.P. could be extracted from the E.E.P. positive serum by ether but not by chloroform. After it was extracted by ether, however, E.E.P. became chloroform-soluble. 2. When the serum was acidified after the ether extraction of E.E.P., a yellow pigment could be extracted again by ether, which was found to be the indirect reacting bilirubin. 3. The E.E.P. positive jaundiced serum was observed to contain much direct reacting bilirubin even after the ether extraction of E.E.P. 4. The lipid stain positive substance could be extracted by ether in a great quantity at a time, which it could not be extracted by chloroform. This substance was considered to play an important role in E.E.P. positive phenomena. 5. E.E.P. was presumed to combine with β-globulin through the combination of the lipid stain positive substance with β-globulin in the serum. 6. By comparing proteins in E.E.P. positive serum by paper electrophoresis before and after the ether extraction of E.E.P., it was found that β-globulin decreased considerably after this extraction. This fact also confirmed that the lipid stain positive substance could be extracted by ether, because this substance was combined with β-globulin. 7. For examining the presence of E.E.P., it was found to be better to observe the diazo layer after the direct diazo reaction than to examine the ether extract. 8. The E.E.P. positive jaundiced serum did not necessarily result from carcinomatous biliary obstruction but from a severe intrahepatic or extrahepatic biliary obstruction independently of its cause.