The formation of reactive oxygen species (ROS) plays an important role in the pathology of vascular diseases. In this study we investigated effects of the novel Nox-inhibitor 3-benzyl-7-(2- benzoxazolyl)thio-1,2,3-triazolo[4,5-d]pyrimidine (VAS2870) on oxidized low-density lipoprotein (oxLDL)-mediated ROS formation in human umbilical vein endothelial cells (HUVEC). VAS2870 has been identified as a inhibitor of NAD(P)H oxidases by high throughput screening. The structure of VAS2870 was characterized by NMR and mass spectrometry. HUVECs were cultured to confluence and ROS formation was induced with 50 mg/ml oxLDL for two hours. OxLDL induced ROS formation in human endothelial cells (171±12%). This augmented ROS formation was completely inhibited by VAS2870 (101±9%). Similar results were obtained with SOD (91±7%). The expression of the major endothelial Nox isoform Nox4 was measured in response to nLDL, oxLDL, and VAS2870. Native and oxidized LDL did not change the Nox4 mRNA expression. Furthermore, Nox4 mRNA expression level was not changed by VAS2870 (5 mM) alone in human endothelial cells for up to 24 hours. We conclude that VAS2870 could provide a novel strategy to inhibit the augmented endothelial superoxide anion formation in response to cardiovascular risk factors.