Nitric oxide (NO) has been suggested to play an important role in endotoxin-mediated shock and inflammation. In this study, we investigated the effect of Rosa laevigata Michx. (Rosaceae) on the production of NO and the molecular mechanism of its action. Rosa laevigata inhibited NO generation and iNOS expression in LPS-stimulated murine macrophages. Activity of nuclear $factor{-kappa}B;(NF{-kappa}B)$ and the degradation of $I{kappa}B-{alpha}$ were suppressed by Rosa laevigata. Furthermore, extracellular signal-stimulated kinase (ERK), which is known to be involved in $NF{-kappa}B$ activation, is inhibited by Rosa laevigata. These results suggest that Rosa laevigata could exert its anti-inflammatory actions by suppressing the synthesis of NO through inhibition of $NF{-kappa}B$ activity.