A number of ectomycorrhizal (ECM) fungi, from sites uncontaminated by toxic metals, were investigated to determine their sensitivity to Cd2+, Pb2+, Zn2+ and Sb3−, measured as an inhibition of fungal biomass production. Isolates were grown in liquid media amended with the metals, individually (over a range of concentrations) and in combination (at single concentrations) to determine any significant interactions between the metals. Significant interspecific variation in sensitivity to Cd2+ and Zn2+ was recorded, while Pb2+ and Sb3− individually had little effect. The presence of Pb2+ and Sb3− in the media did however, ameliorate Cd2+ and Zn2+ toxicity in some circumstances. Interactions between Cd2+ and Zn2+ were investigated further over a range of concentrations. Zn2+ was found to significantly ameliorate the toxicity of Cd2+ to three of the four isolates tested. The influence of Zn2+ varied between ECM species and with the concentrations of metals tested.