Constitutively expressed Fas ligand (FasL) in several distinct epithelial cell types appears to protect tissues by inducing apoptosis of Fas+ immune cells during inflammatory reactions. To study the rela-tionship of FasL and inflammation process in cornea,we examined the effects of inflammatory cytokine IL-1β on the FasL production,expression and cytotoxic function in corneal endothelial cells. In this paper,we demonstrate that IL-1β inhibits the FasL production and expression in corneal endothelial cells. The promoter activities of FasL in these cells are reduced by IL-1β in a dose-dependent manner. Finally,we also find that IL-1β block the cytotoxic effects of FasL derived from corneal endothelial cells to the Fas+ target cells. These data support the view that FasL derived from corneal endothelial cells modulate inflammation within cornea. Constitutively expressed Fas ligand (FasL) in several distinct epithelial cell types appears to protect tissues by inducing apoptosis of Fas + immune cells during inflammatory reactions. To study the rela-tionship of FasL and inflammation process in cornea, we examined the effects of inflammatory cytokine IL -1β on the FasL production, expression and cytotoxic function in corneal endothelial cells. We show that IL-1β inhibits the FasL production and expression in corneal endothelial cells. The promoter activities of FasL in these cells are reduced by IL- 1β in a dose-dependent manner. Finally, we also find that IL-1β block the cytotoxic effects of FasL derived from corneal endothelial cells to the Fas + target cells. These data support the view that FasL derived from corneal endothelial cells modulate inflammation within cornea .