The tapeworm Moniezia expansa and naturally infected sheep were investigated with respect to their cadmium accumulation. Cadmium chloride (CdCl(2), 0.2 g) was added to 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week. The cadmium content of M. expansa was lower than that in the liver tissues of sheep, although this difference was not significant. The highest mean cadmium concentrations were found in the liver of sheep infected with M. expansa (24.5+/-11.5 mgkg(-1) dry weight). The mean cadmium concentration measured in M. expansa was 21.5+/-19.2 mgkg(-1) dry weight, which was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but 0.9 times lower than levels determined in the liver of host. Sheeps with M. expansa infection always had higher cadmium concentrations in the tissues (with the exception of the blood) than their uninfected conspecifics.