The decolorization of two different textile dyes, Reactive Red 2 and Reactive Blue 4, was studied in batch as well as continuous experiments using Bjerkandera sp. Strain BOL 13. The batch experiments were performed to study the decolorization of the dyes separately as well as in a mixture. The results from the experiments showed that the fungus decolorized both dyes. The absorbance was measured at 538 and 595 nm, the peak absorbance wavelengths of the red and blue dyes respectively. The absorbance decreased with 99% at both 538 and 595 nm in the experiments in which the dyes were studied separately at a concentration of 100 mg/l. The corresponding figure for the experiment in which the dyes were studied in a mixture was 98%. A continuous rotating biological contactor was then used to study the decolorization of mixtures of the two dyes at three different concentrations, e.g. 50, 100 and 200 mg/l of each of the dyestuff. The decrease in absorbance at 538 nm was 96% at the two lower dye concentrations while it was 81% at the highest concentration. The corresponding figures at 595 nm were 94 and 80%. The hydraulic retention time was 3 days. Scanning of the absorbance between 200 and 800 nm showed that three peaks disappeared in the UV range during treatment (246, 283 and 323.5 nm) and that a new plateau was formed around 270 nm. (c) 2005 Elsevier Inc. All rights reserved.