Sequences of partial 18S rDNA have been analyzed to elucidate genetic diversity of scallops collected around Korean sea, The scallops used in genetic comparison are Argopecten irradians concentricus, Amusium japonicum japonicum, Chlamys farreri farreri, Chlamys (Swiftopecten) swifti and Patinopecten yessoensis. The 18S rDNA sequences were aligned by Clustalx program. Phylogenetic tree was drawn by Treecon program, The scallops were divided into two groups-the Family Pectinidae containing A. japonicum japonicum and the Family Propeamussiidae containing Argopecten, Chlamys and Patinopecten genera. The Family Propeamussiidae was also divided into the Supergenera Aequipecten containing A. irradians concentricus and Supergenera Chlamys containing C. farreri farreri, C. swifti and P. yessoensis. The species of C. swifti was closer to the P. yessoensis rather than C. farreri farreri in respect to nuclear 18S rDNA sequence.