trans-Resveratrol (Res), a phytoalexin found at high levels in grapes and in grape products such as red wine, has been shown to have anti-inflammatory and antioncogenic properties. Because the transcription factor nuclear factor kappaB (NF-kappaB) is involved in inflammatory diseases and oncogenesis, we tested whether Res could modulate NF-kappaB activity. Res was shown to be a potent inhibitor of both NF-kappaB activation and NF-kappaB-dependent gene expression through its ability to inhibit IkappaB kinase activity, the key regulator in NF-kappaB activation, likely by inhibiting an upstream signaling component. In addition, Res blocked the expression of mRNA-encoding monocyte chemoattractant protein-1, a NF-kappaB-regulated gene. Relative to cancer chemopreventive properties, Res induced apoptosis in fibroblasts after the induced expression of oncogenic H-Ras. Thus, Res is likely to function by inhibiting inflammatory and oncogenic diseases, at least in part, through the inhibition of NF-kappaB activation by blocking IkappaB kinase activity. These data may also explain aspects of the so-called "French paradox" that is associated with reduced mortality from coronary heart disease and certain cancers and provide a molecular rationale for the role of a potent chemopreventive compound in blocking the initiation of inflammation and oncogenesis.