The gene which encodes growth hormone releasing hormone (GHRH) arose from an ancestral gene that also gave rise to the genes for vasoactive intestinal peptide (VIP), pituitary adenylyl-cyclase activating polypeptide (PACAP), glucagon, and secretin. Review of the GHRH gene sequence predicts a second 30 amino acid carboxyl terminal peptide product that has a high degree of homology with VIP and PACAP. This novel peptide, which we have called GHRH-related peptide (GHRH-RP), has been previously localized to rat testicular germ cells. GHRH-RP activates Sertoli cell expression of stem cell factor. Although GHRH is produced by a variety of rat tissues, including the hypothalamus, placenta, testis, and ovary, GHRH-RP has only been described in the testis. We sought to determine if this novel peptide is present in the cycling rat ovary.