Fifty-eight fungi from different physio-ecological groups were compared for their capacity to oxidize five polycyclic aromatic hydrocarbons (PAH) with three to five benzene rings (R), and produce the appertaining extracellular oxidoreductases in liquid culture. In 14 d, wood- and straw-associated basidiomycetes converted 19–90% of the original PAH compounds. The groups of wood- and straw-degrading, wood-degrading, terricolous, ectomycorrhizal, and mitosporic fungi converted PAH at a proportion of 100[ratio ]75[ratio ]34[ratio ]19[ratio ]18. All fungi preferred fluoranthene and pyrene (4R). Anthracene (3R) was preferred by wood-associated fungi. Phenanthrene (3R) and perylene (5R) were sufficiently converted by wood-associated and terricolous, but poorly by ectomycorrhizal and mitosporic fungi. Nevertheless, fungi that converted the entire set of PAH satisfactorily were found in all five groups. PAH conversion was correlated with the production of manganese peroxidase (r=0·98), peroxidase (r=0·89), and laccase (r=0·85), but not with monophenol monooxygenase (r=0·07). Mn(III) ions oxidized all PAH with preference to anthracene. Hydrogen peroxide converted PAH possibly by the products of Fenton's reaction. Limiting factors were shortages in peroxidases and H2O2. Gymnopilus sapineus and Agrocybe praecox converted top quantities of PAH in the absence of peroxidases, manganese peroxidases, and lignin peroxidases. The relative contributions of intra- and extracellular enzymes to the conversion of PAH and the possible role of the fungi in the long-term detoxification of soil xenobiotics are discussed.