Interferon-γ (IFN-γ) has been implicated in liver damage in animal models and chronic hepatitis C infection; however, the underlying mechanism is not clear. Here we examined the role of STAT1, a key signaling molecule for IFN-γ, in a model of murine hepatitis induced by the injection of LPS/d-galactosamine and in human hepatoma Hep3B cells. STAT1 is rapidly activated and highly induced after injection of LPS/d-galactosamine. Both overexpression of STAT1 and hepatocellular damage are located in the same pericentral region. Disruption of the STAT1 gene abolishes LPS/d-galactosamine-induced liver injury. Studies from IFN-γ-deficient mice indicate that IFN-γ is the major cytokine responsible for activation and hyperexpression of STAT1 in LPS/d-galactosamine-induced hepatitis. Hep3B cells overexpressing dominant negative STAT1 are resistant to IFN-γ and IFN-γ + TNF-α-induced cell death, whereas Hep3B cells overexpressing wild-type STAT1 are more susceptible to cell death. Taken together, these findings suggest that STAT1 plays an essential role in LPS/d-galactosamine-induced liver apoptosis and injury.