A new method for immuno-affinity purification of specific antibodies against human gastrin releasing peptide(h-GRP) was developed. The antiserum GP(No. 6201) elicited by h-GRP-BSA conjugate was heterogeneous and reacted not only with h-GRP and its fragments but also partially with other structurally related peptides, such as other GRPs (porcine, canine, and chicken), bombesin, and neuromedin-C. To obtain specific antibodies against human GRP, antiserum GP was purified by column chromatography on the amino-terminal octapeptide h-GRP(1-8)-linked polydimethylacrylamide resin. The antibody thus obtained was highly specific to amino-terminal sequence of h-GRP and hardly reacted with other GRPs (porcine, canine and chicken), bombesin, and even carboxy-terminal h-GRP fragments in ELISA.