This study investigated the potential use of the mushroom Agaricus macrosporus for bioextraction of heavy metals from contaminated substrates. Mushrooms were grown (1) in a noncontaminated control substrate, (2) in a substrate with added Cd (10 mg per kg dw), and (3) in a multi-contaminated substrate (Cd, Hg and Ph each at 10 mg kg(-1); Cu and Zn each at 20 mg kg(-1)). Metal contents were determined in fruiting bodies by anodic stripping voltammetry (ASV). In the control substrate, three production waves ('breaks') were obtained, compared with only two in the contaminated substrates; however, total biomass in the Cd-contaminated substrate was similar to that in the control substrate, and only 40% lower (ie still considerable) in the Hg-containing multi-contaminated substrate. Within each break, metal contents were higher in young than in adult individuals. Metal contents were also higher in the hymenophore than in other parts of the fruiting body. The metal content data indicate that A macrosporus effectively extracted Cd, Hg and Cu (though not Pb) from the contaminated substrates. Of particular interest is the tolerance and extraction of Hg, in contrast with plants. These results suggest that fungi such as A macrosporus may be effective for bioremediation of metal-contaminated substrates, though bearing in mind that in many contaminated environments cultivation of mushrooms of this type may be difficult. (C) 2005 Society of Chemical Industry.