Objectives : The present study was examined to evaluate the anti-inflammatory effects of the Humulus japonicus MeOH extracts (HJE) in vivo. Methods : The effects of HJE on anti-inflammation were measured by production of NO, iNOS (inducible Nitric Oxide Synthase), COX-2, I$kappa$B$alpha$ (Inhibitor kappa B alpha), NF$kappa$B (Nuclear Factor kappa B), TNF-$alpha$ (Tumor Necrosis Factor-alpha) and IL-1$eta$ (Interleukin-1$eta$), IL-6 in Raw 264.7 macrophage cells stimulated with LPS. Results : 1. All concentrations of HJE(0.03 and 0.10 mg/ml) had no significant cytotoxicity in Raw 264.7 cell during the entire experimental period. 2. The level of NO and iNOS in culture medium was dramatically increased by LPS application. However, these increases were dose-dependently(0.03 and 0.10 mg/ml) attenuated by treatment with HJE. 3. HJE extract reduced PGE2 levels in a dose-dependent manner as a consequence of inhibition of COX-2 protein expression in Raw 264.7 macrophage cells stimulated with LPS. 4. 0.10 mg/ml HJE significantly inhibited the phosphorylation of I$kappa$B$alpha$ indicating the suppression of NF-$kappa$B pathway in Raw 264.7 macrophage cells stimulated with LPS. 5. 0.10 mg/ml HJE significantly inhibited the production of TNF-$alpha$ in Raw 264.7 macrophage cells stimulated with LPS. 6. All concentrations of HJE significantly inhibited the production of IL-1$eta$, IL-6 in Raw 264.7 macrophage cells stimulated with LPS. Conclusions : These results provide evidences that therapeutic effect of HJE on heat syndrome, especially due to the acute inflammation, are partly due to the reduction of some of inflammatory factors by inhibiting iNOS and COX-2 through the suppression of p-I$kappa$B$alpha$. Moreover, it suggests that the mechanism of action of HJE comes from the suppression of inflammatory mediators, such as NO, PGE$_2$ and pro-inflammatory cytokines.