Manganese peroxidase (MnP) activity in 10 day old cultures of Trametes versicolor 290 increased from 13 to 104 nmol/ml.min when the nitrogen concentration in the growth medium was increased from 0.1 to 0.4 gL(-1) and supplemented with 600 mu M Mn(II). When cultured under these conditions the fungus oxidised the PAHs fluorene and phenanthrene, with approximately 75% oxidation of phenanthrene after 11 days incubation and complete oxidation of fluorene after 7 days.