Relatively high decolourisation of bleach plant effluent (41%-48%) could be attained in short treatment times using biomass of Rhizomucor pusillus, a mucoralean fungus. Cell wall fractions (alkali-resistant, residual and chitosan fractions) extracted from the R pusillus biomass appeared to be mainly responsible for the adsorption of chromophores from bleach plant effluent by this fungus. The alkali-resistant fraction removed 34% of the colour from bleach plant effluent. Although the residual and chitosan fractions represented only about 12% of the total dry biomass, they removed more colour from bleach plant effluent (41%) than did the intact biomass (39%). The chitosan and residual cell wall fractions, mainly composed of chitin and/or chitosan, seem to be involved in the mechanism of colour removal from bleach plant effluent by R pusillus.