Nuclear factor-kappaB (NF-kappaB) is a critical transcription factor for maximal expression of many of the cytokines that are involved in the pathogenesis of inflammatory diseases. In this study, we found that pinosylvin, a natural stilbenoid that is a component of the pine leaf (Pinus densiflora), significantly inhibited LPS-induced NF-kappaB activation in a concentration-dependent manner. Additionally, pinosylvin was found to inhibit the LPS-induced phosphorylation and degradation of IkappaB alpha in THP-1 cells. Therefore, we have attempted to determine whether pinosylvin can inhibit the expression of cytokines possessing NF-kappaB binding sites in their promoter regions. In a consistent result, pinosylvin inhibited LPS-induced production of TNF alpha and interleukin-8 (IL-8). Taken together, these results show that pinosylvin suppresses the production of pro-inflammatory mediators through the inhibition of the NF-kappaB signaling pathway.