By means of Ouchterlony's immunodiffusion method and immunoelectrophoresis the author analyzed fluorocarbon-extracted antigens from spleens and livers from 30 C 58 leukemic mice (16 myelogenous, 14 lymphocytic) and obtained the fellowing results. 1) Immunoelectrophoresis of normal antigens showed the presence of at least 2~5 precipitate components in the region of albumin, α-and β-globulin of normal serum. 2) The precipitate line specific to lymphocytic leukemic antigen was observed in the region of α-globulin of normal serum. This line was found in 4 of 14 cases. 3) The precipitate line specific to myelogenous leukemic antigen was observed in the region of β-globulin of normal serum. It was found in 8 of 16 cases. 4) The precipitate line common to both lymphocytic and myelogenous leukemic antigens but absent in normal antigen was found in the region of β-globulin of normal serum. It was detected in 8 of 14 lymphocytic leukemic cases and in 11 of myelogenous leukemic cases. 5) Staining of these lines specific to viral mouse antigens revealed that these precipitate lines contained proteins consisted of mucoprotein, glycoprotein and a trace of lipoprotein. The amount of DNA, however, was considered very small or entirely absent.