In order to assess the effects of metal interactions on trace elements uptake, a greenhouse experiment was conducted, in which chinese cabbage was grown for 55 days in a soil to which copper and zinc were added singly and in combination. Plant growth was measured as shoot and root dry matter production. At the end of the experiment the plant material was analysed for metal uptake and the soil was extracted with 0.1N HCl solution, to measure the plant-available metal content. The most consistent effect on plant growth was an interaction between copper and zinc, which was also important in determining uptake of these metals and the amounts extractable with HCl solution. An analysis of the underlying mechanism led to the conclusion that the growth of chinese cabbage was controlled principally by the amount of plant-available zinc, which depended on the amounts of both added zinc and added copper. The effect of the added copper was to increase the toxicity of the added zinc.