Domoic acid (DA) and DA derivatives are water-soluble neurotoxins produced by a number of marine algae, in particular those of the genus Pseudo-nitzschia. This ASP ELISA is specific for DA with no cross-reactivity to non-toxic, structural analogues like kainic acid, L-glutamic acid, L-glutamine, formimino-L-glutamic acid, proline or g-aminobutyric acid (GABA). The assay is primarily intended for use in routine monitoring of DA levels in bivalve molluscs to comply with the regulatory maximum permitted level, but is also applicable for DA quantification in other marine matrices.