2′.4.4′.6′-Tetrahdroxychalcone-2′-glucoside-[β-14C] is incorporated into cyanidin in red cabbage and into cyanidin and quercetin in buckwheat. In all cases no randomization of radioactivity occurs. as was shown by degradation of the compounds. Therefore the chalcone is probably a common precursor of the anthocyanin and flavonol. Furthermore, it can be concluded from the experimental results that the oxidation state of the heterocyclic ring and ring B in the flavanoids is determined at the stage of a chalcone or of a related C15 intermediate.