The value of H+ efflux in assessing and understanding metal interactions with Saccharomyces cerevisiae was investigated for its potential use as a rapid means of toxicity assessment for a range of metals Toxicity decreased in the order Cu2+ > Cd2+ > Pb2+ > Co2+ > Sr2+. Toxic effects can be alleviated by external Ca2+. The effect of Cu2+ and Co2+ on S cerevisiae growth, and the intracellular localisation of Cu2+, were studied in order to gain a better understanding of their toxicity. S cerevisiae, Amorphotheca resinae and Azolla filiculoides biosorbed various metals, with concomitant K+ and Mg2+ release and pH change in certain situations S cerevisiae adsorbed Cu2+ and Cd2+ maximally to ca 150|jmol g'1 and Sr2+ to ca 90|amol g" 1 2 1 2+ 2+ 1 Cu , Cd and Sr were adsorbed maximally to ca 70, 40 and 45|imol g respectively by A resinae. The data were also fitted to the Langmuir and Scatchard adsorption models. Both Cu2+ and Cd2+ were adsorbed to maximum uptake levels o f 350 and 245 ^mol g ‘l respectively by native A filiculoides (Azolla) Native milled-sieved Azolla and epichlorhydrm-immobilised Azolla exhibited Cu2+ uptake levels o f ca 363 and 320|jmol g'1 respectively from solutions with an initial Cu2+ concentration o f lOOmg I"1. Milled-sieved Azolla and epichlorhydrm-immobilised Azolla, along with the native Azolla, successfully biosorbed influent Cu2+ during column studies. Packed bed biosorption columns containing 1Og and 25g of epichlorhydrm-immobilised Azolla were capable of complete removal of metal from ca 4 and 12 litres, respectively, of influent 5mg I'1 Cu2+ Even after 22 litres of influent solution had passed through, the 25g column was still at less than 75% saturation. These columns were more efficient than those containing the same corresponding quantities of milled-sieved Azolla (ca 3 and 105 litres for 10 and 25g columns respectively), which in turn were more efficient than native Azolla (ca 3-4 litres for a 25g column). Selected results were compared to a computer model used to predict column profile The biosorbed Cu2+ was successfully recovered using Chelaton 3.