The histamine release induced by compound 48/80, bradykinin or polyethylenimine with a molecular weight of 600 (PEI₆) was inhibited by wheat germ agglutinin (WGA) and phytohemagglutinin E-subunits (PHA-E₄), and the inhibition was specifically reversed by N-acetyl glucosamine and N-acetyl galactosamine, respectively. Concanavalin A (Con A) and phytohemagglutinin L-subunits (PHA-L₄) did not inhibit the histamine release induced by compound 48/80, bradykinin or PEI₆. The histamine release induced by substance P was also inhibited sugar-specifically by WGA and PHA-E₄. The binding sites for compound 48/80, bradykinin, PEI₆ and substance P, therefore, seemed to especially overlap each other. These binding sites were found to be glycoproteins having affinities to WGA and PHA-E₄, but not to Con A and PHA-L₄. The binding of WGA and PHA-E₄ to the glycoproteins resulted in inhibition of the interaction between the basic secretagogues including bradykinin and substance P and their binding sites on the mast cells. The bindings of five lectins to mast cell glycoproteins were examined by lectin-blotting. Several glycoproteins, which had specific affinities to WGA and PHA-E₄, but not to Con A and PHA-L₄ were detected. We assumed that the binding sites for basic secretagogues which are coupled with histamine-releasing mechanisms exist among these glycoproteins. A 41-kDa protein (α-subunit of pertussis toxin-sensitive G protein) was not detected by WGA, suggesting that the binding sites for the basic secretagogues were not G proteins.