Agitation, temperature, inoculum size, initial pH and pH of buffered medium affected the decolorization of Orange II dye by Coriolus versicolor and Funalia trogii. The optimum temperature and initial pH value for decolorization were 30 degreesC and 6.5-7.0, respectively; pH 4.5 was the most efficient in buffered cultures. High decolorization extents were reached at all agitation rates. At an inoculum size of more than 1 mt, the extent of decolorization changed only slightly. High extents were obtained using immobilized fungi at repeated batch mode.