Three filamentous fungi were examined for the ability to biotransform phenanthrene to oxidative (phase I) and conjugative (phase II) metabolites. Phenanthrene metabolites were purified by high-performance liquid chromatography (HPLC) and identified by UV/visible absorption, mass, and 1H NMR spectra. Aspergillus niger ATCC 6275, Syncephalastrum racemosum UT-70, and Cunninghamella elegans ATCC 9245 initially transformed [9-(14)C]phenanthrene to produce metabolites at the 9,10-, 1,2-, and 3,4-positions. Subsequently, sulfate conjugates of phase I metabolites were formed by A. niger, S. racemosum, and C. elegans. Minor glucuronide conjugates of 9-phenanthrol and phenanthrene trans-9, 10-dihydrodiol were formed by S. racemosum and A. niger, respectively. In addition, C. elegans produced the glucose conjugates 1-phenanthryl beta-D-glucopyranoside and 2-hydroxy-1-phenanthryl beta-D-glucopyranoside, a novel metabolite. [9-(14)C]Phenanthrene metabolites were not detected in organic extracts from biotransformation experiments with the yeasts, Candida lipolytica 37-1, Candida tropicalis ATCC 32113, and Candida maltosa R-42.