Domoic acid (DA) was identified as the toxin responsible for an outbreak of illness in Canada in 1987, caused by eating blue mussels that had accumulated DA as a result of the presence of Pseudo-nitzschia pungens. It is named amnesic shellfish poisoning (ASP). Since a regulatory level of 20 mg DA/kg of shellfish meat was established. The methods of determination of domoic acid are reviewed: biological assays in vivo and in vitro, biochemical and chemical assays. The AOAC mouse bioassay, which is used for PSP, cannot detect domoic acid at the regulatory level of 20 mg/kg tissue and no interlaboratory validation of this method for domoic acid has been carried out. The Quillian method, a liquid chromatography-UV detection method is approved as European Norm by CEN and recommended by Codex Alimentarius as reference method. The European Commission Regulation stipulate that the reference method shall be the HPLC method and the Community Reference Laboratory on Marine Biotoxins (CRLMB) recommends Quillian method as routine method. Others protocols such as receptor binding assay, immunoassays and thin layer chromatography can be used as alternative for routine monitoring. The liquid chromatography-mass spectrometry method allows to confirm the presence of domoic acid isomers.