Resveratrol, a phytoalexin found in grapes and wine, has been shown to have anti-inflammatory properties. Since endothelium is activated during inflammation by some cytokines released by macrophages and many other cells, we tested whether resveratrol could modulate endothelial cell activation. We studied the effect of resveratrol treatment in vitro on the expression of vascular cell adhesion molecule-1 by tumour necrosis factor alpha-stimulated human umbilical vein endothelial cells. In addition, we studied the effect of resveratrol treatment in vivo (in a murine experimental model) on the modulation of tumour necrosis factor alpha-induced vascular permeability. Resveratrol, used at the concentrations present in human plasma following moderate wine consumption, was demonstrated to be an inhibitor of the adhesion molecule expression by tumour necrosis factor alpha-stimulated endothelial cells. In addition, resveratrol significantly prevented the cytokine-induced vascular leakage. Our results (both in vitro and in vivo) may explain some aspects of the anti-inflammatory effects of resveratrol.