The behaviour of the trace elements in biological systems is mostly a reflection of the strong affinity of cellular components for these elements. This behaviour can be modified by changes in the environment of the cell which influence the supply of a particular element available to participate in cellular reactions, by changes which modify cellular components in such a manner that their affinity for the element is increased or decreased, or by changes in the intra-or extra-cellular concentration of elements which compete for a specific binding site. Although in this review we are concerned with nutritional changes that may modify trace-element metabolism in the intact animal we are, in effect, dealing with these reactions. With this in mind I have selected examples of recent advances in knowledge of the influence of the nature of the diet on processes such as the liberation of trace elements from food material, the storage of these elements in the tissues, their incorporation into their functional units in the cell and finally their excretion.