Excessive nitric oxide production by inducible nitric oxide synthase (iNOS) in stimulated inflammatory cells is thought to be a causative factor of cellular injury in cases of inflammation. In recent studies, it has been shown that kahweol, coffee-specific diterpene, exhibit chemoprotective effects. In this study, we investigated the effects of kahweol on the production of and the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. The nitrite production induced by LPS was markedly reduced in a dose-dependent manner. In addition, kahweol suppressed the expression of iNOS protein and iNOS mRNA. Since iNOS transcription has been shown to be under the control of the transcription factor, NF-kappaB, the effects of kahweol on NF-kappaB activation were examined. Transient transfection experiments showed that kahweol inhibited NF-kappaB-dependent transcriptional activity. Moreover, electrophoretic mobility shift assay experiments indicated that kahweol blocked the LPS-induced activation of NF-kappaB. The results of these studies suggest that the suppression of the transcriptional activation of iNOS by kahweol might be mediated through the inhibition of NF-kappaB activation. Taken together, the results of our study provide evidence that kahweol possess an anti-inflammatory potential, which constitutes a previously unrecognized biologic activity, and which may provide new insights into the inflammatory process.