The present study on the classification and description of the marine mesogastropods based on the materials which were collected during the period from 12th to 17th of July in 1989 at nine localities of the Ullug Island. Seven unrecored species in 6 families of mesogastropodes are new to the fauna of Ullung Island. As a result of this study, 7 families and 8 species of marind mesogastuopoes are riported from the Ullung Island. Two species of thim, Costalynia costulata(Dunker, 1860), Barleeia angustata(Pilsbry, 1901), are found to be new to the fauna of Korea.