Spleen cells from BALB/c mice immunized against Echinococcus multilocularis were fused with mouse myeloma cells (P3X6.5.3.) in the presence of polyethylene glycol (PEG 1000), and the hybridomas were obtained. Of the 85 hybridomas, 23 were found to produce antibodies. Of the 23 cell lines, 13 hybridomas which produced a high titer of antibodies were cultured for cloning the cells by the limiting dilution method. Then 5 monoclonal antibodies were obtained. The immunoglobulin class of the monoclonal antibodies were IgM in one, IgG in 4. IgG monoclonal antibodies were studied by the ABC immunostain method. The germinal layer, brood capsules and protoscolices were stained. Germinal layer was especially stained by 4 monoclonal antibodies. However sections of liver, kidney, spleen and other parasites; anisakis, ascariasis lumbricoides, entamoeba histolytica and schistosoma japonicum were not stained with those monoclonal antibodies.