The components of paralytic shellfish poisons produced by toxic plankton Protogonyaulax tamarensis from Funka Bay, Hokkaido, were investigated.The cells of P. tamarensis cultured in BSW-4 medium were extracted with 80% ethanol (pH 2.0). The extract was defatted with chloroform, and then purified by two types of column chromatography on Bio-Gel P-2 and Bio-Rex 70 (H+). The toxins thus obtained were analyzed by using cellulose acetate membrane electrophoresis and thin layer chromatography on silica-gel.From the toxic fractions unbound on Bio-Rex 70 column, four components coded tentatively as PTX₁, PTX₂, PTX₃ and PTX₄ were detected. Judging from Rm values, Rf values and the result of acid-hydrolysis, PTX₁ and PTX₂ were demonstrated to be gonyautoxin-8 and its epimer, respectively. On the other hand, from the toxic fractions bound on Bio-Rex 70 column, gonyautoxins 1-4, neosaxitoxin and saxitoxin were detected.