The biosorption of lead(II) by fruiting bodies of Pleurotus ostreams immobilized in calcium alginate was studied. The experimental results showed that the fruiting bodies were effective in removing Pb(II) from solution. Biosorption equilibrium was approached within 45 min. Pseudo second-order was applicable to all the sorption data over the entire time range. Intra-particle diffusion was not the only rate-determining step. The sorption data conformed well to both the Langtnuir and the Freundlich isotherm model. The maximum adsorption capacity (q(max)) onto P. ostreatus immobilized in calcium alginate was 121.21 mg g(-1) for Pb(II). The FT-IR analysis showed that the mechanism involved in biosorption of Pb(II) by fruiting bodies of P. ostreatus was mainly attributed to Pb(II) binding of amide I group. (c) 2005 Elsevier Ltd. All rights reserved.