The rDNAs of figh-killing dinoflagellates Cochlodinium polykrikoides and Karlodinium veneficum were detected from the East China Sea by species-specific real-time PCR probes. Sequence analysesusing the partial ITS sequences from the real-time PCR products showed identical sequences with C. Polykrikoides and K. veneficum, respectively and low expectation values (E-value) of less than 1e-5 suggesting the presence of these organisms in the East Ching Sea shelf water that flows into the Tsushima Strait and the Yellow Sea.