Endothelial cell activation is achieved by the rapid, protein synthesis-independent induction of a characteristic set of genes. Because of the abundance of binding sites for the transcription factor NF-κB in the regulatory region of the aforementioned genes, we hypothesized that this factor might play a key role. Reactive oxygen intermediates act as second messengers in the activation of NF-κB. We have used the antioxidant pyrrolidine dithiocarbamate to analyze the effect of NF-κB inhibition on TNFα-induced EC activation in vitro. We show that pyrrolidine dithiocarbamate strongly reduces the TNFα-mediated induction of E-selectin, VCAM-1, ICAM-1, PAI-1, tissue factor, IL-8 and IκB-α. We present evidence identifying NF-κB as a central regulator of EC activation. Therefore, this factor may represent a prime target for therapeutic intervention in pathologic conditions associated with EC activation such as allo- and xenograft rejection, atherosclerosis, ischemic reperfusion injury and vasculitis.