From the early stage of pancreatic adenocarcinoma in hamsters and also of hepatocellular carcinoma in rats, induced by treatment withN-nitrosobis (2-oxopropyl)amine and 3′-methyl-dimethylaminoazobenzene, respectively, hepatic levels of metallothionein (MT) were found to be continuously elevated. In the hepatoma-induced rats, this elevation preceded that of serum γ-glutamyl transpeptidase activity, a marker enzyme for hepatocellular carcinoma. These results indicate that, in the course of chemical carcinogenesis, the elevation of hepatic MT level occurred and continued from the early stage of carcinogenesis. This type of elevation of hepatic MT level was also observed in lung metastasis-induced mice. On the other hand, in rats with pancreatitis caused by the administration of deoxycholate, the hepatic level of MT rose only transiently.