Human data on the effects of diet composition on intestinal cadmium uptake are almost completely lacking but animal experiments indicate that it may profoundly influence the intestinal uptake of ionic cadmium. Thus, rats and mice fed human dietary items absorbed 5-8 times more cadmium than animals fed ordinary rodent pellets. All the data currently available indicates that, both in humans and in experimental animals, the bioavailability of dietary cadmium is not very different from that of ionic cadmium. However, diet composition may markedly affect the uptake of the latter. Accordingly, a valid assessment of the bioavailability of cadmium can be made in experiments where ionic cadmium is administered mixed with the diet. It is important, however, to discriminate between diet composition at the time of administration and dietary status. A better understanding of the factors affecting intestinal cadmium uptake is necessary in assessing the risk associated with dietary cadmium exposure and further studies are therefore urgently needed.