The Glucagon Antibody was raised to glucagon coupled to bovine thyroglobulin with glutaraldehyde. The antibody has a proven strong Biotin-Streptavidin/HRP immunostaining at a 1/500-1/1000 dilution in human pancreatic islets. Staining is completely eliminated by pretreatment of the diluted antibody in an excess of glucagon. Preadsorption of the diluted antibody with an excess of the following substances had no effect on glucagon labeling: secretin, vasoactive intestinal peptide, peptide histidine isoleucine-27, gastric inhibitory polypeptide, rat and human growth hormone releasing hormone and somatostatin.