In this study, the graft copolymerization of methacrylic acid onto the biomass of baker's yeast was carried out in aqueous medium using potassium persulfate (PPS) as initiator. The poly (methacrylic acid) modified biomass obtained was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and microscopic analyses. The number of functional groups was determined by potentiometric titration. The adsorption capacity of the modified biomass for Pb2+, Cd2+ and Cu2+ showed a significant increase compared with the pristine biomass, due to the presence of a large number of functional groups. According to the Langmuir equation, the maximum uptake capacities (q(m)) for Pb2+, Cd2+ and Cu2+ were 243.9, 108.7 and 73.5mg g(-1), respectively. Adsorption kinetics study showed that completion of the adsorption process needed only 30 min. The loaded biosorbent was regenerated using EDTA solution and used repeatedly three times with little loss of uptake capacity. Good results were obtained when the modified biomass was used to treat simulated wastewater containing Pb2+, Cd2+ and Cu2+. (c) 2007 Society of Chemical Industry.