The influence of a 28-week treatment with disulfiram (DSF), D-penicillamine (PA), and nitrosodiethylamine (NDEA), as well as with a combination of DSF or PA with NDEA on the concentrations of eight essential trace elements in the whole liver tissue of rats was measured by means of neutron activation analysis. While NDEA treatment lowered the Zn content of the liver, DSF alone or in combination with NDEA enhanced the Zn and Se concentration by 50%-80%. Co, Cu, and Cd levels were increased by factors of 10, 60, and 110, respectively. The Mo concentration was decreased by 50% after DSF administration. PA reduced Cu, Co, and Zn in the liver. PA/NDEA treatment also lowered Cu, Co, and Zn content, but there was no strengthening effect of PA on the decrease in Zn observed with NDEA. The change of trace element concentrations, especially of Cu, is discussed with regard to the observed tumor induction in the liver, which tended to be increased by a combined NDEA/PA administration compared with NDEA treatment alone, whereas a protective action of DSF against NDEA induced liver tumors could not be established.