Liver fibrogenesis resulting from a diversity of pathological changes involves a disturbance in mineral, in particular zinc, homeostasis. The present study was undertaken to determine whether gene therapy with metallothionein (MT), a small protein critically involved in the regulation of zinc homeostasis, can improve the recovery of liver fibrosis in a mouse model. Wild-type (WT) mice treated with carbon tetrachloride in corn oil twice a week at 1 ml/kg for 4 weeks developed a reversible liver fibrosis upon removal of the chemical, correlating with a high level of hepatic MT; but those treated for 8 weeks developed an irreversible liver fibrosis along with low levels of hepatic MT. The same carbon tetrachloride treatment for 4 weeks resulted in an irreversible liver fibrosis in MT-knockout (MT-KO) mice. Adenoviral delivery of the human MT-II gene (approved symbol MT2A) through intravenous injection reversed the fibrosis along with increased hepatocyte regeneration within 3 days in both WT and MT-KO mice with irreversible fibrosis. The MT elevation was associated with increased activities of collagenases in the liver. This study indicates that MT makes a critical contribution to the reversal of chemical-induced hepatic fibrosis and has therapeutic potential for patients with certain liver fibrosis.