—High plasma levels of VLDL are associated with increased risk for atherosclerosis. Here we show that VLDL (75 to 150 μg/mL) activates nuclear factor-κB (NF-κB), a transcription factor known to play a key role in regulation of inflammation. Oxidation of VLDL reduced its capacity to activate NF-κB in vitro, whereas free fatty acids such as linoleic and oleic acid activated NF-κB to the same extent as did VLDL. Intravenous injection of human VLDL (6 mg protein per kg) into rats resulted in arterial activation of NF-κB as assessed by electrophoretic mobility shift assay. Aortic endothelial cells showed positive nuclear staining for the activated RelA (p65) subunit of NF-κB at 6 to 24 hours after injection. There was also a parallel expression of the adhesion molecules intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, as well as the cytokine tumor necrosis factor-α. Pretreatment of the rats with diet containing 1% of the antioxidant probucol for 8 weeks did not inhibit arterial activation of NF-κB in response to injection of VLDL. Moreover, injection of triglycerides (10% Intralipid, 5 mL/kg) activated arterial expression of NF-κB to the same extent as VLDL. Our results suggest that VLDL may promote the development of atherosclerotic lesions by activation of the proinflammatory transcription factor NF-κB. The effect appears to be mediated by a release of VLDL fatty acids but not to involve VLDL oxidation.