A cDNA clone encoding a novel mRNA (harderin) has been isolated from the cDNA library of frog Rana esculenta Harderian gland. The cDNA is 875 bp long and encodes a novel protein of 218 amino acid residues. The deduced proteins reveals no significant homology to other proteins. The mRNA is a single 0.9 kb transcript detected only in the RNA of frog Harderian gland, highly expressed throughout the year. The constant and exclusive presence of harderin in the frog Harderian gland, suggests a constitutive tissue specific expression for this protein.