Vascular inflammation is an important factor which can promote diabetic complications. Preliminary investigations of several crude plant extracts including aqueous extract of Benincasa hispida Cogniaux exhibit anti-inflammatory properties. This study investigates the mechanism of anti-vascular inflammatory activity of an aqueous extract of B. hispida Cogniaux (ABH) in human umbilical vein endothelial cells (HUVECs). The study was performed on HUVECs that were pretreated with various concentrations (1-20 microg/ml) of ABH before exposure with high glucose (25 mM) for 48 h. Cell ELISA and Western blot analysis showed that ABH inhibited high glucose-induced cell adhesion molecules (CAMs) surface and protein expression, resulting in reduced adhesion of U937 monocytes. ABH also inhibited the mRNA expression level of monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8). High glucose-induced ROS production was inhibited by treatment of ABH. We observed that pretreatment with HUVECs with ABH blocks NF-kappaB activation via blocking phosphorylation and degradation of its inhibitory protein, IkappaB-alpha. ABH also reduced NF-kB promoter activity. These results suggest that ABH reduces high glucose-induced CAMs activation by inhibiting monocyte adhesion, ROS, and NF-kappaB in HUVECs.