Agaricus bisporus contains novel aromatic compounds. By incubation of the mushroom with [G-14 C]shikimic acid, the radioactivity was incorporated into tyrosine, phenylalanine and several unidentified metabolites. The most radioactive metabolite in the stipe and the cap was identified as N-(gamma-L-glutamyl)-4-hydroxyaniline. The radioactivity was proved to be localized in the 4-hydroxyaniline moiety of this compound.