We demonstrate that KIOM-79, combined extracts obtained from Magnolia officinalis, Pueraria lobata, Glycyrrhiza uralensis, and Euphorbia pekinensis, inhibits LPS-induced expression of iNOS gene in RAW 264.7 cells. Treatment of RAW 264.7 cells with KIOM-79 inhibited LPS-stimulated nitric oxide production in a dose-related manner. Immunohisto-chemical staining of iNOS and RT-PCR analysis showed that the decrease of NO was due to the inhibition of iNOS gene expression. Immunostaining of p65, EMSA, and reporter gene assay showed that KIOM-79 inhibited NF-kappa/Rel nuclear translocation, DNA binding, and transcriptional activation, respectively. Western immunoblot analysis of p38 kinase showed KIOM-79 significantly inhibited the phosphoylation of p38 kinase which is important in the regulation of iNOS gene expression. Collectively, this series of experiments indicates that KIOM inhibits iNOS gene expression by blocking NF-kappa/Rel and p38 kinase signaling. Due to the critical role that NO release plays in mediating inflammatory responses, the inhibitory effects of KIOM-79 on iNOS suggest that KIOM-79 may represent a useful anti-inflammatory agent.