Objectives : Achyranthes japonica (AJ) has been used as an anti-bacterial and anti-inflammatory agent. However, it is unclear that AJ could show the anti-inflammatory effects in macrophages. In this experiment, we studied whether AJ could inhibit the inflammatory responses in macrophages. Methods : To measure out the cytotoxicity of AJ, we performed the MTT assay. We evaluated the nitric oxide (NO) production, and cytokine production such as interleukin (IL)-1b, IL-6 and tumor necrosis factor (TNF)-a. We also investigated the cellular mechanims such as mitogen activated protein kinases (MAPK)s and nuclear factor kappa B (NF-kB). Results : AJ inhibited lipopolysaccharide (LPS)-induced NO production. AJ also inhibited production levels of IL-1b, IL-6 and TNF-a in LPS-stimulated macrophage. Finally, western blot analysis showed that AJ treatment inhibited the activation of p38 but not of extracellular signal-regulated kinase, c-jun NH2-terminal kinase and NF-kB. Conclusions : These results showed that AJ down-regulated the inflammatory response via p38 in macrophages, which suggest that AJ could be a candidate on treating inflammatory diseases.