Two monoclonal antibodies (named mAb3G4 and mAb4A2) against recombinant pEL98 protein have been produced. The specificity of the mAbs was verified by immunoblot and immunoprecipitation analyses. To determine cellular localization of the pEL98 protein in NIH3T3 and 3Y1 cells, indirect immunofluorescent staining was performed using mAb4A2. The results showed that most of the pEL98 protein existed diffusely in the cytoplasm, while a part of the protein existed along actin stress fibers in both cells. The expression of pEL98 protein in various murine and human tissues and cells was also examined by immunoblot analysis using mAb3G4. The results demonstrated that the pEL98 protein was expressed in bone marrow, spleen, peritoneal macrophages and human lymphocytes, with the highest amount found in peritoneal macrophages.