Nine metals were analysed in whole specimens of the decapod crustancean Cancer irroratus, and three in the exoskeleton of Carcinus maenas. In terms of concentrations (expressed as parts per millions) and concentration factors, 2 groups of metals could be distinguished in Cancer irroratus: Zn, Cu, Fe and Mn in one group, Ca, Mg, Sr, Na and K in the other group. Na excepted, all the metals had concentration factors significantly higher (P<0.01) than="" 1.="" the="" concentration="" factor="" of="" na="" was="" significantly="" lower=""><0.01) than="" 1,="" demonstrating="" the="" existence="" in="">C. irroratus of a barrier to the movement of Na into the crustacean from its environment. Studies of coefficients of discrimination (D), in C. irroratus, for metals considered in pairs, showed, in each case that D was significantly different (Plt;0.01) from 1. Only the discrimination factor between, Zn and Mn was less significantly different (0.05lt;Plt;0.1) from 1. Correlations were made between the concentrations of metals and other parameters: water content, size, and ash content. Significant correlations were found, especially in the cases of the pairs Ca–Sr, Na–K, Cu–Zn, and Mn-animal size.