When canine tracheal explants were incubated in culture medium 199 in the presence of D-glucosamine labeled with carbon-14 for 24 hours, a significant amount of radioactivity was found in the secreted macromolecules. When kallidin was present in the culture medium, the amount of radioactivity associated with a portion of these macromolecules was increased. A met-lys-bradykinin derivative had a similar effect, but bradykinin did not. When hexadimethrine, an inhibitor of kinin formation, was present in the culture medium, the amount of radioactivity in the macro-molecular fraction was decreased. Substance P and the structurally related polypeptides, physalaemin and eledoisin, also enhanced the production of tracheal macromolecules; they were several-fold more active than kallidin. The effect of polypeptides on the activities of glycosyltransferases was also investigated. One of the enzymes present in a microsomal fraction prepared from the mucosal lining of canine trachea was uridine diphosphate (UDP)-galactose:mucin galactosyltransferase, which required a 25 mM concentration of maganese ions to be present in the assay mixture to obtain maximal enzymatic activity. When the concentration of manganese ions was decreased to 2.5 mM, there was less than one third of the maximal enzymatic activity, but full activity could be restored by the addition of kallidin. Several other basic polypeptides had a similar effect on the enzymatic activity. Kallidin had little or no effect on the activities of several other glycosyltransferases. The results suggest that basic polypeptides may be important in controlling the synthesis and/or release of respiratory glycoproteins.