Some 17 strains of filamentous fungi, encompassing 13 different species, were tested for their ability to decolorize the polymeric dye R-478. Decolorization was observed with both living and dead mycelia of the three Aspergillus species tested, indicating bioadsorption, not biodegradation. With mycelia of other strains tested, the most decolorization was obtained with Marasmiellus troyanus, Pleurotus sapidus, and Pleurotus ostreatus; with extracellular filtrates, the most decolorization was observed with Laetiporus sulphureus. Parallel experiments incubating benzo[a]pyrene (B[a]P) with mycelia and filtrates showed that six of the species removed over 40% of B[a]P in comparison with HgCl2-killed controls. The highest B[a]P removal by mycelia was shown by M. troyanus (95.0%); the highest level by extracellular filtrates was shown by Hericium erinaceous (44.8%). With the exception of A. ochraceous, no products of B[a]P metabolism were detected for any of the species tested. For most species, the disappearance of B[a]P was correlated with the ability to decolorize poly R-478 (r = 0.78 for mycelia; r = 0.74 for culture fluids). M. troyanus gave rise to more disappearance than decolorization. The removal of B[a]P by M. troyanus and Phanerochaete chrysosporium was compared over 30 days : M. troyanus gave significantly better removal in a biphasic pattern.