The ability of the white rot fungus Trametes trogii BAFC 463 (high producer of ligninolytic enzymes, especially laccase and manganese peroxidase) to degrade the dye anthraquinone blue, refractory to bacterial attack, was evaluated. Both tropho- and idiophasic T. trogii cultures in synthetic medium (glucose/asparagine) and complex medium (malt extract/glucose) were able to transform up to 88% dye in 4 hours. The activity of laccase, an oxygen-dependent phenoloxidase which was present at high levels in all the conditions assayed, might be related to the ability of the fungus to degrade the colorant. This is supported by the fact that in bioreactor experiences carried out at pH 4.5 the addition of anthraquinone blue caused a decrease in the levels of soluble oxygen. However, although high levels of laccase were produced at pH 7.5, the enzyme was not active, and neither dye transformation nor loss in the levels of soluble oxygen were quantified.