Monitoring of the contaminations of the endocrine disrupting chemicals (EDCs) was carried out in coastal areas of Korea and Japan using wild grey mullet (Mugil cephalus). The results show that some individuals in Korea and Japan were influenced by environmental EDCs. Moreover, the obtained cDNA fragment of estrogen receptor (ER) α of grey mullet was 2294bps long, but the N-terminal region was unidentified in the deduced amino acid residue of this cDNA. The DNA binding domain and the ligand-binding domain of the deduced amino acid residues of ERα in grey mullet showed high homology with other ERs.