Biosorption of heavy metals was carried out using whole mycelia and selected components of Aspergillus niger, Rhizopus oryzae and Mucor rouxii. Binding of copper, cadmium, nickel and zinc was considerably improved by treating the cell wall fraction with 4 M NaOH at 121 degreesC. Chitosan contributed most to the biosorptive capacity. 0.96 mmol copper was bound by 1 g of the treated mycelium of M rouxii DSM 1191.