A series of 12 monoclonal antibodies was made against mucous and serous components of rhesus monkey trachea. These antibodies were used to localize secretory products in the respiratory epithelium by immunohistochemical methods. Mucous cells of the tracheal surface epithelium and submucosal glands were shown by histochemical methods to be a homogeneous population containing periodate-reactive sulfated glycoconjugates. Immunohistochemical staining using the monoclonal antibodies on glycol methacrylate sections serial to those stained histochemically revealed a more antigenically heterogeneous population of secretory cells. Four distinct staining patterns were observed with the 12 monoclonal antibodies. Eight antibodies reacted with most, but not all, mucous and serous cells. Two antibodies recognized subpopulations of secretory cells. One antibody stained tracheal mucous cells with a concentration of reaction product on the luminal border, and one antibody stained only serous cells within the glands. Ten of the 12 antibodies were shown to react in an ELISA with the high molecular weight void volume containing mucous glycoproteins separated on a Sepharose CL-4B gel filtration column. None of the antibodies recognized blood group antigens. We conclude: (1) that production of a large panel of monoclonal antibodies to respiratory tract mucins from primates is feasible, (2) that the monoclonal antibodies will recognize epitopes on biochemically identifiable glycoproteins, and (3) that the intracellular mucous products of tracheal secretory cells exhibit greater heterogeneity than is detectable by conventional histochemistry.