The biodegradation of chloronaphthalene (CN) and polycyclic aromatic hydrocarbons by the white-rot fungus Phlebia lindtneri, which can degrade dichlorinated dioxins and non-chlorinated dioxin-like compounds, was investigated. Naphthalene, phenanthrene, 1-chloronaphthalene (1-CN) and 2-chloronaphthalene (2-CN) were metabolized by the fungus to form several oxidized products. Naphthalene and phenanthrene were metabolized to the corresponding hydroxylated and dihydrodihydroxylated metabolites. 2-CN was metabolized to 3-chloro-2-naphtol, 6-chloro-1-naphtol and two other chloronaphtols, CN-dihydrodiols and CN-diols. Significant inhibition of the degradation of these substrates was observed when they were incubated with the cytochrome P-450 monooxygenase inhibitors 1-aminobenzotriazole and piperonyl butoxide. These results suggest that P. lindtneri initially oxidizes these substrates by a cytochrome P-450 monooxygenase.