Endothelial synthesis of NO is catalyzed by constitutive NO synthase type III (NOS-III). NOS-III has been thought to be regulated mainly at the level of enzyme activity by intracellular calcium. We report that in human umbilical vein endothelial cells lysophosphatidylcholine (lyso-PC), a component of atherogenic lipoproteins and atherosclerotic lesions, increases NOS-III mRNA and protein levels. This leads to the augmentation of NOS-III activity and the enhancement of antiplatelet properties of endothelial cells. Importantly, nuclear run-off experiments demonstrate a transcriptional mechanism of regulation of NOS-III expression by lysophosphatidylcholine. As endothelium-derived NO appears to be an anti-atherogenic molecule, induction of NOS-III by lyso-PC may be a protective response that limits the progress of the atherosclerotic lesion and promotes its regression.