assay was designed and evaluated for rapid detection and quantification of the toxic algae. A pair of specific primers was designed from the sequence of ITS1 regionof which the PCR specificity was examined compared with the other nine dinoflagellates. PCR amplifications were detected only from samples which containedand specific signals were not detected from any other microalgae. Based on crushed algae by ultrasound for the standardwas 0.989. Moreoverthat had been cultured in different conditions could be quantified in agreement with the quantification by optical microscopy.