This document specifies a method for the quantitative determination of saxitoxin (STX), decarbamoyl saxitoxin (dcSTX), neosaxitoxin (NEO), decarbamoyl neosaxitoxin (dcNEO), gonyautoxin 1 and 4 (GTX1,4; sum of isomers), gonyautoxin 2 and 3 (GTX2,3; sum of isomers), gonyautoxin 5 (GTX5 also called B1), gonyautoxin 6 (GTX6 also called B2), decarbamoyl gonyautoxin 2 and 3 (dcGTX2,3; sum of isomers), N-sulfocarbamoyl-gonyautoxin 1 and 2 (C1,2; sum of isomers) and (depending on the availability of certified reference materials (CRMs)) N-sulfocarbamoyl-gonyautoxin 3 and 4 (C3,4; sum of isomers) in (raw) mussels, oysters, scallops and clams. Laboratory experience has shown, that it is also be applicable in other shellfish [10], [13] and cooked shellfish products. The method described was validated in a collaborative study [1], [2] and published as AOAC Official Method [3]. This method was also verified in a EURL-performance test aiming the total toxicity of the samples [4]. Toxins which were not available in the first collaborative study [1], [2] as dcGTX2,3 and dcNEO were validated in two additional studies [5], [6]. The lowest validated levels [1], [2], [6], are given in µg toxin (free base) per kg shellfish meat and also as µmol/kg shellfish meat and are listed in Table 1. A quantitative determination of GTX6 (B2) was not included in the first study but several laboratories detected this toxin directly after the ion exchange clean-up and reported a mass concentration of 30 µg/kg or higher in certain samples. For that reason, the present method is applicable to quantify GTX6 (B2) directly, depending on the availability of the standard material. Currently it is possible to determine GTX6 after a hydrolysis as NEO. The indirect quantification of GTX6 was validated in two additional studies [5], [6]. A quantitative determination of C3,4 was included in the first study. The present method is applicable to quantify C3,4 directly, depending on the availability of the standard material. The same hydrolysis protocol used for GTX6 can be applied to Fraction 1 of the SPE-COOH if C3,4 is present, to quantify this toxin as GTX1,4 [8].