Vascular endothelial dysfunction and subsequent inflammation underlie many pathological diseases such as cardiovascular disease, diabetes, and hypertension. Both events are principally initiated by reduced endothelial-derived nitric oxide (NO) bioavailability and/or activation of vascular/leukocyte NADPH oxidase. NADPH oxidase has 7 isoforms (NOX1-5 and Duox1-2). We currently have limited knowledge regarding the roles of individual NOX isoforms in diseases, particularly NOX1, which is a major NADPH oxidase isoform in the vasculature but not in leukocytes. In this study, we evaluated the roles of NOX1 in vascular endothelial dysfunction-induced inflammation by recording leukocyte rolling, adherence, and transmigration in a postcapillary venule of rat mesenteric tissue in real time via intravital microscopy. We superfused the mesenteric tissue with Krebs™ buffer, and Krebs™ buffer with a non-selective NO synthase inhibitor, NG-nitro-L-arginine-methyl-ester (L-NAME, 50 µM) with/without a selective NOX1 inhibitor, ML171. We found that at 2 hrs of superfusion, leukocyte rolling (21±8 cells/min), adherence (3±2 cells/100 µm), and transmigration (2±1 cells/200 µm2) was minimal in Krebs™ control (n=8). By contrast, L-NAME (n=6) significantly increased leukocyte rolling (74±12), adhesion (19±6), and transmigration (18±4) (all P<0.05 compared to Krebs™ control). Whereas, ML171 (1 µM, n=7) prevented the L-NAME-induced effect on leukocyte rolling (25±5), adhesion (5±2), and transmigration (5±1). These findings suggest that NOX-1 activation participates in L-NAME induced inflammatory responses; whereas inhibition of NOX1 can mitigate inflammation following vascular endothelial dysfunction.