As a cytosolic transcription factor, the aryl hydrocarbon (Ah) receptor is involved in several pathophysiologicalevents leading to immunosuppression and cancer; hence antagonists of the Ah receptor maypossess chemoprevention properties. It is known to modulate carcinogen-metabolising enzymes, for instancethe CYP1 family of cytochromes P450 and quinone reductase, both important in the biotransformation ofmany chemical carcinogens via regulating phase I and phase II enzyme systems. Utilising chemically-activatedluciferase expression (CALUX) assay it was revealed that intact glucosinolates, glucoraphanin and glucoerucin,isolated from Brassica oleracea L. var. acephala sabellica and Eruca sativa ripe seeds, respectively, are suchantagonists. Both glucosinolates were poor ligands for the Ah receptor; however, they effectively antagonisedactivation of the receptor by the avid ligand benzo[a]pyrene. Indeed, intact glucosinolate glucoraphanin was amore potent antagonist to the receptor than glucoerucin. It can be concluded that both glucosinolates effectivelyact as antagonists for the Ah receptor, and this may contribute to their established chemoprevention potency.