8 species of shellfish which were collected from Jiangsu and Zhejiang Provinces in Feb. 1992 , were detected for okadaic acid by high performance liquid chromatography with 92chloromethylanthracene (92CA) and tetramethylammonium hydroxide ( TMAH) . The result showed that the range of okadaic acid content is from 15. 75～218. 95ng·g -1 , and the average of content is 37. 10ng·g -1. 48 % samples were detected okadaic acid , and the content of one sample was beyond the critical limit (200ng·g 1) . It suggests that the diarrhetic shellfish poison is widely distributed in China , and shellfish from some areas contain high toxicity.