This paper presents the results of a study on the content of Cu, Zn, Pb and Cd in livers and breast muscles of mallards obtained in Warmia and Mazury in 1999-2000. Samples from 32 mallards hunted in Łężany, Zembrze, Szestno and Nidzica, as well as samples from 7 pheasants and 6 mallards from the area of Śląsk were analyzed. Concentration of all the four metals was higher in the liver than in breast muscles. Mean contents of copper in livers of juvenile and adult mallards from Warmia and Mazury were similar (6.567 and 8.632 mg/kg w.w.). Levels of zinc were approximately the same in both age groups (23.911 mg/kg w.w. in young birds and 25.418 mg/kg w.w. in adults). As regards lead, older mallards from Warmia and Mazury had twice as much of the metal in the liver (0.417 mg/kg w.w.). The content of Pb in the liver was similar in both age groups of the birds from Śląsk. The differences in the concentration of cadmium in the mallards from Warmia and Mazury were smaller. Cd in the amount of 0.128 mg/kg m.m. was found in the young mallards and 0.171 mg/kg m.m. in the adult mallards. The birds from the area of Śląsk contained much higher concentrations of Cd in their tissues, over 1 mg/kg m.m. in the liver and over 0.200 mg/kg m.m. in the breast muscles.