Objective : This study was performed to evaluate the effect of Forsythiae Fructus (FF) ethanol extract on inflammatory cytokine production and its underlying mechanisms in mouse macrophages. Methods : Peritoneal macrophages from thioglycollate medium-injected mice were cultured and stimulated with lipopolysaccharide(LPS) or LPS/interferon(IFN)-${gamma}$ for cytokine measurement and cellular signaling molecule analysis. Results : FF ethanol extract decreased the levels of secreted tumor necrosis factor(TNF)-${alpha}$ and interleukin(IL)-6 in IFN-${gamma}$/LPS-stimulated cells in a concentration-dependent manner. FF extract reduced IFN-${gamma}$/LPS-induced STAT1 phosphorylation and LPS-induced p38 and JNK activation, but not ERK1/2 activity. The extract also inhibited LPS-induced $I{kappa}B{alpha}$ degradation through suppression of $I{kappa}B{alpha}$ kinase. Conclusions : These results suggest that FF ethanol extract affects the production of TNF-${alpha}$ and IL-6 through inhibition of activation of STAT-1, $I{kappa}B{alpha}$, p38, and JNK.