Endotoxin (LPS) has been established to induce hepatic metallothionein (MT), but the specific role of MT remains unknown. In this study, we examined whether MT can modulate MTF-1 activity during endotoxemia. Treatment with IL-6, the main mediator of MT induction during endotoxemia, enhanced the expression of the MRE(d)-driven reporter gene. MTF-1 DNA-binding activity was increased 16-24 h after LPS administration in wild-type mice, while no such activation was observed in MT-null mice during the same period. The expression of alpha(1)-acid glycoprotein (AGP) mRNA, an RNA regulated by MTF-1, was lower in MT-null than in wild-type mice. Our results suggested that MTF-1 was activated during endotoxemia. MT can act as an activator of MTF-1, and MT can induce MTF-1 targeted gene expression during endotoxemia.