The native and treated fungal biomass of Phanerocheate chrysosporium was used for the biosorption of a textile dye (i.e., Reactive Blue 4). In the batch system, the biosorption equilibrium time was about 4 h and the maximum dye uptake on all the tested fungal biomass preparations was observed at pH 3.0. The dye uptake capacities of the biosorbents at 600 mg L-1 dye concentration were found to be 132.5, 156.9, 147.6 and 81.1 mg g(-1) for native and heat-, acid- and base-treated dry fungal preparations, respectively. The dye uptake capacity order of the fungal preparations was found as heat-treated > acid-treated > native > base-treated. The Langmuir, Freundlich and Temkin adsorption models were used for the mathematical description of the biosorption equilibrium. The Freundlich and Temkin models were able to describe the biosorption equilibrium of Reactive Blue 4 on native and treated fungal preparations. The dye biosorption on the fungal biomass preparations followed Ritchie kinetic model. Biosorption of the dye from aqueous solution was also investigated in a continuous flow system. The maximum biosorption capacity of the heat-treated fungal biomass P chrysosporium was 211.6 mg (g dry biomass)(-1) at an initial dye concentration of 600 mg L-1 and at a flow rate of 20 mL h(-1). (c) 2006 Elsevier B.V. All rights reserved.