The effect of piceatannol on lipopolysaccharide (LPS)-induced nitric oxide (NO) production was examined. Piceatannol significantly inhibited NO production in LPS-stimulated RAW 264.7 cells. The inhibition was due to the reduced expression of an inducible isoform of NO synthase (iNOS). The inhibitory effect of piceatannol was mediated by down-regulation of LPS-induced nuclear factor (NF)-kappaB activation, but not by its cytotoxic action. Piceatannol inhibited IkappaB kinase (IKK)-alpha and beta phosphorylation, and subsequently IkappaB-alpha phosphorylation in LPS-stimulated RAW 264.7 cells. On the other hand, piceatannol did not affect activation of mitogen-activated protein (MAP) kinases including extracellular signal regulated kinase 1/2 (Erk1/2), p38 and stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK). Piceatannol inhibited the phosphorylation of Akt and Raf-1 molecules, which regulated the activation of IKK-alpha and beta phosphorylation. The detailed mechanism of the inhibition of LPS-induced NO production by piceatannol is discussed.