The concentration of metallothionein in mouse tissues after administration of ascorbic acid was determined by the Cd-hem method. The concentration of metallothionein in the liver was increased significantly after an intraperitoneal injection of L-ascorbic acid at the dose of 1000 mg/kg. A simultaneous injection of cycloheximide inhibited the increase of the metallothionein concentration. Mortality of mice injected with a lethal dose of cadmium was decreased significantly by the pre-injection of L-ascorbic acid. All of these results indicate that metallothionein is induced in the liver after the administration of ascorbic acid.