Four freshwater algae with different cell surface characteristic, Oscillatoria limnetica, Anabaena spiroides, Eudorina elegans and Chlorella vulgaris, were chosen to examine their copper(II), cadmium(II) and lead(II) (copper, cadmium, and lead cations with a charge of 2+) sorption activity using the Freundlich model, in terms of the surface area/dry weight ratios, and the presence of other metal ions. Experimental data obeyed the Freundlich model, indicating multiple functional binding sites on algal surfaces. All four algae showed the highest sorption capacity for Pb among three metals. Their sorption activity varied with initial metal concentrations. The surface area/dry weight ratio was demonstrated to be a major parameter determining the sorption activities and mechanisms of algae. However, no apparent relationship occurred between metal-binding ability and, the presence and amount of mucilage. Competition of metal ions on algal surface binding sites was found differed with algal species and metal ions. The high and significantly different sorption activities for three metals by four algae suggested the suitability and good selectivity for treatment of different kinds of industrial effluents. (C) 2002 Elsevier Science Ltd. All rights reserved.