The two tandem P450 monooxygenase genes (pc-1 and pc-2) reported by us earlier in Phanerochaete chrysosporium were investigated for their regulation under nutrient-limited and nutrient-rich culture conditions. Transcript analysis based on real-time quantitative RT-PCR showed higher expression of pc-1 in defined low-nitrogen and pc-2 in defined high-nitrogen media, with maximum expression on day 4, indicating that the two genes, though tandemly linked, are regulated in a non-coordinate manner. Transcript levels of pc-1 and pc-2 were differentially influenced by the type of carbon source, incubation temperature, and oxygenation. Both genes were inducible by organic xenobiotic chemicals. Of the 42 xenobiotics tested in nutrient-rich cultures, pc-1 transcription was induced 2.12(+/-0.40)-fold to 6.27(+/-0.48)-fold in the presence of 19 compounds and pc-2 transcription was induced 2.00(+/-0.73)-fold to 29.39(+/-9.40)-fold in the presence of 22 compounds. Particularly, it is significant that both pc-1 and pc-2 are induced by polycyclic aromatic hydrocarbons (PAHs) of varying ring size, including naphthalene (4.35+/-0.09, 6.02+/-1.39), phenanthrene (2.82+/-0.12, 2.14+/-0.61), pyrene (3.93+/-0.01, 1.0+/-0.12), benzanthracene (1.67+/-0.03, 6.08+/-1.50), and benzo(a)pyrene (1.55+/-0.01, 5.54+/-2.75) respectively. This study constitutes the first report on the identification of P450 genes in a fungus that are responsive to environmentally significant pollutant chemicals (PAHs, DDT, long-chain alkyl phenols) and lignin derivatives.