Decolorization of various dyes by pellets of white rot fungi was studied. All fungal pellets used could remove more than 75% of the color of these dyes in 24 h. Effect of various conditions such as initial pH, concentration of dye, amount of pellet, temperature and agitation on Astrazone blue dye decolorization activity of Funalia trogii was tested and the longevity of this decolorization activity under optimum conditions was investigated in repeated-batch mode. An increase in the amount of pellet positively affected the longevity of the decolorization activity while a decrease in dye decolorization capability of pellets occurred with increasing dye concentration in repeated-batch mode. Spectrophotometric and microscopic examinations of F trogii pellets showed that the process involved decolorization through microbial metabolism but not biosorption. The effect of glucose concentration and cheese whey on longevity of decolorization activity was also tested. The percentage of decolorization at a dye concentration of 264 mg/l remained high after 10 days operation especially in culture media with cheese whey. This study showed that white rot fungal pellets could effectively be used as an alternative to the traditional physicochemical process. (C) 2002 Elsevier Science Ltd. All rights reserved.