Marine algal varieties Ascophyllum nodosum, Lessonia flavicans, Laminaria hyperborea and Durvillea potatorum as well as processed seaweed residues arising from the algin extraction industry have been evaluated for toxic metal sorption. Biosorption isotherms have been obtained for copper, cadmium and nickel at controlled solution pH4. Potentiometric titrations and esterification of algal biomass indicate that carboxylate groups are: primarily responsible for metal sorption. Proton/metal interactions play an important role in the biosorption process. Swelling of biosorbents is discussed in the context of potential large-scale fixed-bed column applications.