The biochemical basis for resistance to metal ion toxicity is emerging though it is complicated by the different resistance mechanisms. Several strategies for resistance to toxic metal ions have been identified: The development of energy driven efflux pumps which keep toxic element levels low in the interior of the cell. Such mechanisms have been described for Cd(II) and As(V). Oxidation (e.g. AsO2‐ to AsO4 3‐) or reduction (e.g. Hg2+ to Hg0) can enzymatically and intracellularly convert a more toxic form of an element to a less toxic form. The biosynthesis of intracellular polymers which serve as traps for the removal of metal ions from solution such as traps have been described for cadmium, calcium, nickel and copper. The binding of metal ions to cell surfaces. The precipitation of insoluble metal complexes (e.g. metal sulfides and metal oxides) at cell surfaces. Biomethylation and transport through cell‐membranes by diffusion controlled processes. In this short review I shall discuss the implications o...