As a part of chemical study on the bioactive metabolites from marine organisms, we have investigated cytotoxicity using brine shrimp bioassay for each solvent fractions of the marine algae(12 species), marine sponges(3 species), coelenterates(2 species), echinoderms(4 species), marine molluscs(17 species), and ascidians(2 species), respectively. As the results, chloroform extract of Stichopus japonicus (LC$_{50}$ : 274 $mu extrm{g}$/ml), ethyl acetate extract of Anthocidaris crassispina(LC$_{50}$ : 121 $mu extrm{g}$/ml), n-butanol extract of Unda), ia Pinnatifida (LC$_{50}$ : 178 $mu extrm{g}$/ml), and water extract of Thais clavigera (LC$_{50}$ : 61 $mu extrm{g}$/ml) displayed the most significant cytotoxic activity against brine shrimp. Among the marine organisms tested, echinoderms and marine molluscs were thought to be the most active Phylums on screening of new bioactive compounds.