Hydroxylation of dibenzo-p-dioxin (DD), dibenzofuran (DF), biphenyl (BP) and diphenyl ether (DPE) by the white-rot fungus Phlebia lindtneri GB-1027 was studied. DD and DF were rapidly degraded in a culture of R lindtneri. The initial oxidation products were identified by gas chromatography-mass spectrometry. R lindtneri oxidized DD to 2-hydroxy-DD, and DF to 2- and 3-hydroxy-DF. BP and DPE were also oxidized to p-hydroxy-BP and p-hydroxy-DPE, respectively. The oxidation catalyzed by P. lindtneri with each substrate was position-specific, because the hydroxyl group was introduced to the molecular edge of every substrate. Significant inhibition of the degradation of DD and DF was observed in incubation with the cytochrome P-450 monooxygenase inhibitors I-aminobenzotriazole and piperonyl butoxide. These experiments with cytochrome P-450 inhibitors, and formation of the mono-hydroxyl metabolites suggest that P lindtneri initially oxidizes DD, DF, BP, and DPE by a cytochrome P-450 monooxygenase and that it directly introduces a hydroxyl group to each of these substrates.