This study was done to evaluate the quality of offshore waters in Korea using gametes, embryos and early development system of Asterina pectinifera. Results of the quality evaluation of offshore waters of Korea by bioassay using A. pectinifera has shown that in spite of an inflow of many rivers from Korean topography, the west coast has maintained the second grade (II), because pollutant inflow was decreased due to purification of inflow rivers, control of waste water discharge, construction of wastewater treatment plants, and because pollution was decreased by smooth circulation of sea water with difference of the large ebb and flow of the tide. On the other hand, Asan, Hampyeung and Cheunsu Bay where water circulation is relatively poor, and Gunsan and Mokpo harbors which are inflowed by rich polluants from neighboring cities have shown third grade(III) because A. pectinifera was inhibited violently to early development. The South coast has maintained the second grade (II) or third grade(III) because A. pectinifera was inhibited moderately or strongly to early development. Also, Kangjin, Duekyang, Kwangyang, Masan and Jinhae Bay where water circulation is relatively poor have shown third grade (III) because A. pectinifera was inhibited violently to early development. The East coast has maintained the first and second grade (I), (II) because of simple coasts and smooth circulation of sea water. But Cheungcho Lake was worsened by he breakwater that was constructed in order to maintain port functions.