A marrow stromal osteogenic cell line (MBA-15) was used to create monoclonal antibodies (MoAbs). In this study, we describe a series of MoAbs for mouse marrow stroma (MMS) (MMS-25/17, MMS-85/12, MMS-302/40, and MMS-319/4) that recognized antigens expressed by stromal cells including osteoblastic cells. The MoAbs were screened against various cell and tissue types. MMS-85/12 was positive in detecting an antigen that was highly abundant in osteoblastic cells and primary adherent bone marrow cultures (BMC) but was negative for the marrow adipocytes copartner. The MMS-85/12 MoAb is an IgGl immunoglobulin. The immunohistochemical staining pattern is suggestive of the antigen being associated with the osteoblasts' plasma membrane and with the extracellular matrix constituent secreted by these cells. Western blotting and immunoprecipitation indicated that the antigen that was recognized by MMS-85/12 apparently had a molecular weight of 84 dD.