Indigenous fungi isolated from soil of a former gasworks site were investigated in submerged cultures with pyrene as the sole carbon source. Five fungal strains capable of degrading pyrene included one strain of Trichoderma harzianum and four strains with characteristics of the genus Penicillium. These are identified as Penicillium simplicissimum, Penicillium janthinellum, Penicillium funiculosum and Penicillium terrestre. A maximum of 75% of 50 mg l(-1) and 67% of 100 mg l(-1) of pyrene was removed by the fast degrading strain P. terrestre at 22 degrees C during 28 days of incubation. The slower degrader P. janthinellum was able to remove 57% of 50 mg l(-1) and about 31.5% of 100 mg l(-1) pyrene. Degradation of pyrene is directly correlated with biomass development. To the best of our knowledge, this is the first time that fungi have been reported to use pyrene as the sole carbon and energy source. They may be ideal candidates for effective bioremediation of polycyclic aromatic hydrocarbons.