Antibodies were raised against anisole binding protein, a previously reported constituent of olfactory epithelium. Immunoglobulin containing the antibodies is a potent inhibitor of the mouse EOG,less than 1 ng being sufficient to reduce the responses to odorants by about 50%. This suggests that anisole binding protein is a constituent of the apical cell membranes in the olfactory mucosa and that it has a role in olfactory transduction. The fact that the antibodies inhibit responses to various odorants suggests that odor receptor proteins represent a class of membrane proteins in which there is a portion of the molecule common to all and a variable region in which the specificity resides. Thus, immunization with any would result in antibodies directed against all.