Recent studies support beneficial effects of polyphenols in various chronic inflammatory diseases, for example, the inflammatory bowel diseases. Inhibition of NF-κB activation by polyphenols could explain part of their anti-inflammatory properties, but few data are available on the intestine. The purpose of the present study was thus to investigate the effects of some polyphenols on NF-κB activation using human intestinal Caco-2 cells. Effects of standard polyphenols (50 μmol/l) were studied on different cellular events associated with NF-κB activation: (i) NF-κB activity using cells transiently transfected with a NF-κB–luciferase construct and stimulated by inflammatory agents (IL-1β, TNF-α or lipopolysaccharides (LPS)); (ii) phosphorylation of the inhibitor of κB (IκB-α) analysed by Western blot; (iii) secretion of IL-8 quantified by ELISA assay. Results showed that chrysin and ellagic acid inhibited NF-κB activity, whereas genistein and resveratrol increased it. These effects were independent of the nature of the inducer, indicating that polyphenols may modulate NF-κB activation by acting on a common event to the cytokine- and LPS-mediated cascades. Chrysin strongly reduced (2·5-fold) IL-1β-induced IκB-α phosphorylation, whereas ellagic acid increased it (1·7-fold). Ellagic acid, genistein and epigallocatechin gallate reduced (4- to 8-fold) IL-1β-induced IL-8 secretion, while resveratrol promoted (1·7-fold) the secretion. Chrysin also diminished IL-8 secretion by 1·6-fold (but P>0·05). The data indicate that polyphenols can modulate the NF-κB activation pathway in the intestine. Chrysin could block NF-κB activation via the inhibition of IκB-α phosphorylation. The other molecular targets of the active polyphenols are still to be identified.